The great playing field sell off?

Summary

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More or Less: "The Great Playing Field Sell Off?"

BBC Radio 4 — August 17, 2012

Episode Overview

This episode, hosted by Tim Harford, explores several debated statistics from recent news and political discourse. Central themes include the accuracy of claims about the number of UK school playing fields sold off (contextualized in light of the post-Olympics focus on sporting legacy), the impact of 20 mph speed limits on road safety statistics, issues in the calculation of inflation figures (the quirks of the UK’s Retail Price Index - RPI), and a conversation with Daniel Tammet, author and mathematical savant, about numbers and imagination.

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1. The School Playing Field Sell-Off: Digging into the Numbers

Segment starts at 00:42

Key Discussion Points

• Headlines versus Reality: Recent headlines claimed up to 30 school playing fields had been sold by the coalition government, while the government previously cited 21. There’s alarm about what this means for the “Olympic legacy.”

  • Charlotte Macdonald [00:52]: “Olympic legacy, 21 school fields sold off in two years revealed the 30 school playing fields sold off by the Coalition.”

• Unpacking Old Claims: The widely quoted figure is that 10,000 school playing fields were sold between 1979 and 1997 under Conservative governments, but its source is murky.

  • Tim Harford [01:58]: "Between 1979 and 1997, under the previous Conservative government, an estimated 10,000 playing fields were sold off."
  • Wesley Stevenson [02:07]: “This 10,000 number has been quoted all over ... but there's a bit of a mystery here… in 2007, the claim became 10,000.”

• Provenance of the Numbers: Earlier claims were for 5,000 fields; this abruptly changed to 10,000 with no clear source in government documentation.

  • Wesley Stevenson [02:32]: “We've no idea where the department got the number ... [They now say] the number's mere speculation.”

• How the 5,000 Figure Was Constructed:

  • Snapshots in the early 1980s captured fields "under threat," not actual sales.
  • Extrapolations assumed all schools sold fields at the same rate as grant-maintained schools during a particular period, then generously halved and rounded figures.
  • Alison Morguin (Fields In Trust) [03:45]: “There was a snapshot done ... which put it at 5,000 ... only a snapshot. ... It's very difficult to know how many exactly ...”

• Anecdotal vs. Actual Evidence: There's consensus that "thousands" were lost, but no credible or systematic count exists for pre-1998 sales. Since 1998, sales are officially counted, but there's still uncertainty about the totals.

  • Wesley Stevenson [06:19]: “If anyone tells you they know for sure how many, don't believe them. The truth is that the number of playing field sales has only been counted since 1998.”

• Important Context: Many field sales coincide with school closures—a factor both recent and former governments cite in defense.

  • About 3,000 schools closed in England from 1979–1997, largely due to demographic changes.
  • Wesley Stevenson [07:06]: “Around 3,000 schools closed ... that will probably account for at least some of the school playing fields lost ...”

Notable Quote

• Tim Harford [06:43, wryly]: “Another zombie statistic?”

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2. Genealogy, Exponential Ancestors, and Biblical Lineages

Segment starts at 07:31

Key Discussion Points

• Listener Question: With Solomon reputed to have had 700 wives and 300 concubines, could nearly everyone in Jesus's time lay claim to King David as an ancestor?
• Yan Wong’s Explanation:
  • Genealogy expands exponentially, but due to overlapping (shared) ancestors, everyone in a population after sufficient generations is related.
  • By 35 generations (about 1,000 years), everyone in a population of a million would share almost all their ancestors.
  • Yan Wong [11:16]: "If you trace everyone back in Israel at the time of Jesus to 35 generations previous, then they would share all their ancestors in common, which would be about 80% of the total population of Israel at the time, including David..."
• Resolution: Virtually everyone in Israel during Jesus’s time could, with genealogical legitimacy, claim descent from King David.

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3. 20 mph Speed Limits and Road Casualty Statistics

Segment starts at 12:24

Key Discussion Points

• Media Claim: Reports said that casualties "soared" in 20 mph zones, with apparent increases cited (like a 17% rise in deaths).
• Statistical Reality:
  • Actual deaths rose from 6 to 7 nationwide in 20 mph zones from 2010 to 2011; a 17% increase in very small numbers is statistically meaningless.
  • Charlotte Macdonald [13:36]: "There were six deaths in 2010 and seven in 2011."
• The Bigger Picture:
  • Sharp rises in incidents correspond with big expansions in 20 mph zones. For example, Bristol increased from about 50 to about 500 such roads between 2009–2011, and casualties rose in lockstep.
  • Tim Harford [15:26]: “... the number of 20 mile an hour roads increased roughly tenfold ... the number of accidents on them also increased roughly tenfold.”
• Direct Impact?:
  • Bristol's pilot saw positive behavior changes (lower speeds, more cycling, local support), but too few casualties to prove any safety impact.
  • London data (from a British Medical Journal study) more robustly found casualty reductions in 20 mph zones.
  • Dr. Angela Raffle (Public Health Consultant, Bristol) [16:43]: “We cannot learn anything yet from Bristol's pilot on whether it has anything to do with casualties ... But there was a very detailed study from London ... They found a reduction in severity of casualties.”

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4. The Retail Price Index (RPI): Flaws in Inflation Calculations

Segment starts at 17:57

Key Discussion Points

• Background: RPI (Retail Price Index) is a key UK inflation measure, affecting wages, pensions, and fares.
• Clothing Price Conundrum: A methodological change in how clothing prices are sampled led to odd outcomes—at one point, RPI recorded clothing inflation at 12%, the alternative CPI at just 2%, using identical source data.
  • Chris Giles (Financial Times) [19:31]: "RPI clothing price inflation was about 12% and CPI clothing price inflation was 2%, a 10 percentage point difference."
• Underlying Issue: RPI uses an outmoded formula (the Carli index), which averages price changes in a way that always biases results upwards, even if prices return to their starting points.
  • Tim Harford [20:41]: “You might think that not much has changed. But the Carli index averages a 25% price rise for the shirt and a 20% price fall for the blouse and concludes that prices rose 2.5%.”
• Real-World Consequences:
  • Many financial products and government payments are linked to RPI—so systematic overstatements in RPI lead to higher-than-intended fares, pensions, and other payments.
  • Chris Giles [22:17]: “...when we look back ... incomes haven't grown very much. Well, they've actually grown considerably more than we thought by half a percentage point a year ... So the good news is that actually life has got better, although we probably banked all that...”

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5. Daniel Tammet: Numbers, Imagination, and Being “Between Worlds”

Segment starts at 22:48

Key Discussion Points

• Daniel Tammet’s Approach to Numbers:

  • Describes his mind as seeing colors, shapes, and beauty in numbers; has used numbers to bridge from social awkwardness into human connection.
  • Daniel Tammet [23:13]: “The connections have gone to different parts of the brain that maybe other brains don't have... I've learned to find a way of putting feet in both worlds, the world of numbers and the world of people.”

• On Education:

  • Tammet argues that education often crushes children's natural curiosity and imagination for numbers, which is the true heart of mathematics.
  • Daniel Tammet [25:26]: “...schools seem to do so much to work the imagination out of them. And we need to show that mathematics is all about imagination. It's the science of imagination.”

• Memorable Anecdotes:

  • Learned Icelandic in a week; recited 22,514 digits of π as a “poem.”
  • Sees mathematics as a universal language and likens numbers to “landscapes full of life, full of beauty.” [24:31]

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6. Brief: Olympic Medal Table Analysis

Segment at 17:24

• The team built a medal projection model based on population and GDP per capita.
• Charlotte Macdonald [17:48]:
  • “Big overachievers include Team GB, China, the US, Jamaica, and Australia.”
  • “Underachievers are India, Brazil, Indonesia, Pakistan, and Nigeria.”

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Conclusion

The episode exemplifies "More or Less" at its best: lively, skeptical engagement with the numbers that shape public debate. Through detailed analysis and expert insight, it reveals how statistics can be bent or misunderstood—whether on controversial school field sell-offs, the effects of 20 mph speed zones, or hidden quirks in official inflation. Daniel Tammet’s reflections remind listeners of the essential (and too-often-overlooked) human and imaginative side of numbers.

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Notable Quotes Index

• On playing field stats:
  • Tim Harford [06:43]: “Another zombie statistic?”
• On rare events:
  • Charlotte Macdonald [13:36]: "There were six deaths in 2010 and seven in 2011."
• On genealogy:
  • Yan Wong [11:16]: "If you trace everyone back in Israel at the time of Jesus..., then they would share all their ancestors in common... including David..."
• On maths education:
  • Daniel Tammet [25:26]: “…mathematics is all about imagination. It's the science of imagination.”

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Transcript

[Tim Harford]

Hello. I know that some of you are already mourning the loss of a wonderful celebration of talent, training and sheer guts. And it is hard to believe that this series of more or less is nearly over. But we still have almost half an hour of numbersome news, so don't shed a tear just yet. This week are 20 miles an hour speed limits. An unexpected killer. TV's Yan Wong returns to answer your final question and will interview Daniel Tammet, a an author whose mind moves in unusual ways.

[Daniel Tammet]

The connections have gone to different parts of the brain that maybe other brains don't have. I've learned to find a way of putting feet in both worlds, the world of numbers and the world of people.

[Tim Harford]

The Olympics were supposed to inspire a generation to take up sport. No wonder then, that people are depressed about the government's record of selling off school playing fields.

[Charlotte Macdonald]

Olympic legacy, 21 school fields sold off

[Tim Harford]

in two years revealed the 30 school playing fields sold off by the Coalition. Now Wesley Stevenson's here.

[Yan Wong]

Wes.

[Tim Harford]

Whenever we read out a bunch of newspaper headlines, I think I know what's coming next.

[Wesley Stevenson]

A lot of figures have been thrown around about the number of playing fields sold off in England recently, along with allegations about the effect on our Olympic legacy. And today's admission by the government that the number's actually 30 and not 21 hasn't really helped either. But it's worth saying that these figures need a little bit of context, because some of these schools had been closed just under half and others had been merged. Some we don't know what happened to. So these figures might not be quite what they seem. But there's another figure that I want to concentrate on. So let me take you back to the schools of the 1980s and 90s. Here's a figure that's been in the news a lot in the last couple of weeks.

[Tim Harford]

Between 1979 and 1997, under the previous Conservative government, an estimated 10,000 playing fields were sold off.

[Wesley Stevenson]

So this 10,000 number has been quoted all over the media, but also by Labour MPs in Parliament who are keen to accuse the Conservatives of a mass sell off of playing fields during the 80s and 90s. But there's a bit of a mystery here, because I checked HANSARD and these MPs used to say 5,000 playing fields have been sold off between 1979 and 1997. And suddenly in 2007, the claim became 10,000.

[Tim Harford]

So it doubled overnight. Why?

[Wesley Stevenson]

Well, it's a bit odd. I asked one of the Labour MPs who quoted the 10,000 number. Clive Efford, and he pointed me to the 2008 statement from the Department for Culture, Media and Sport, which does include the figure of 10,000, but there's absolutely no paper trail there. We've no idea where the department got the number. The department said at the time that it didn't have the details and the whole business was really the responsibility of the Department for Children's Schools and Families.

[Tim Harford]

And what does that department say?

[Wesley Stevenson]

Well, they're now the Department for Education, and they say that the number's mere speculation.

[Tim Harford]

Ok. So when Labour's in power, we get unsourced claims attacking the Conservatives, and when a Conservative is Minister for Education, those claims are denounced as speculation. I mean, it's all a bit he said, she said, isn't it?

[Wesley Stevenson]

Yes, but although we don't know why it mysteriously doubled to 10,000, we can examine the older claim that 5,000 playing fields were sold off under Margaret Thatcher and John Major, a claim that was made loudly and often by Labour MPs until 2007. I asked Alison Morguin, chief executive of the charity Fields In Trust, that campaigns to save greenspace is what she made of it. You might have expected her to pick the most alarming statistics she could find, but. But she said that we simply don't know and that the figure of 5,000 has a rather sketchy provenance.

[Alison Morguin]

It's a huge leap from 5 to 10,000. And I think that one of the things that this establishes is that how difficult it is to arrive at a certain figure. There was a snapshot done In, I believe, 1983, which put it at 5,000, that was used by the Labour government, but of course, it was only. That is only a snapshot. At that moment, there were further figures that related to Grant maintained schools, and it is impossible to see exactly what the figure is. I think you can say thousands with confidence, but it's very difficult to know how many exactly there are with your hand on your heart.

[Tim Harford]

So run that past me again. There was some survey done in 1983 and there was some extra information later about Grant maintained schools, and then, hey presto, there was a figure of 5,000 playing fields.

[Yan Wong]

Yeah.

[Wesley Stevenson]

When the Labour government produced its estimate of how many playing fields the Conservatives sold off, it did two things. First, it took this survey from the early 1980s, which, by the way, wasn't a survey of fields sold, this was a survey of fields under threat, and not just school fields either. And then, secondly, it made a hugely heroic set of assumptions in order to extrapolate to a Much higher number. They found that grant maintained schools had sold off 64 fields over the course of a particular 30 month period in the mid-1990s.

[Tim Harford]

And then they assumed, then they assumed

[Wesley Stevenson]

that all schools were selling off playing fields at the same rate as grant maintained schools, which is unlikely because the whole point of grant maintained status is it frees a school of local authority control and gives it more control over its own budget.

[Tim Harford]

Ok, and let me guess, they also assumed that the entire 18 years of conservative government saw playing fields sold off at the same rate as this particular 30 months.

[Wesley Stevenson]

Yeah. And then they divided this number by two, just to be cautious, rounded it liberally, and as you say, hey presto,

[Tim Harford]

they got to 5,000 and the number stuck.

[Wesley Stevenson]

Yeah. Even after the less than convincing calculation had been explained in an answer to a parliamentary question, the Labour government stood by it. And it's been widely quoted ever since. Despite this confession from Baroness Ashton in the House of Lords in 2001, we

[Charlotte Macdonald]

have attempted to work out a guesstimate

[Alison Morguin]

of what we believe.

[Charlotte Macdonald]

We believe that probably somewhere around 30

[Alison Morguin]

to 40 playing fields a month were being sold off.

[Charlotte Macdonald]

This is now my laws comparative to

[Alison Morguin]

something in the order of three. But these are guesstimates and I would

[Charlotte Macdonald]

not wish to be held responsible because we simply do not have the information.

[Wesley Stevenson]

There's plenty of anecdotal evidence to suggest that a lot of school playing fields were sold off in the 1980s and 90s. But if anyone tells you they know for sure how many, don't believe them. The truth is that the number of playing field sales has only been counted since 1998. And even then we have no idea how many there were then or how many there are now.

[Tim Harford]

You know what this is, Wes?

[Yan Wong]

What's that?

[Tim Harford]

Another zombie statistic?

[Yan Wong]

Oh, dear.

[Wesley Stevenson]

I mean, one final point you must remember the current government justified their figures by saying that playing fields have mainly been sold when schools have been closed. The previous government also justifies a significant minority of the playing field sales under their term this way.

[Tim Harford]

So it would probably help if we looked at how many schools were closed between 1979 and 1997.

[Wesley Stevenson]

And if you look at that period, around 3,000 schools closed in England at that time. A lot simply responding to the changes in the birth rate. And that will probably account for at least some of the school playing fields lost during this period.

[Tim Harford]

Well, thank you, Wes. As you might know, TV's Yan Wong has been putting his large brain in the service of more or less listeners. This series offering to answer any question you care to Throw at him. He's here again. Hello, Jan. Hello.

[Chris Giles]

Welcome.

[Tim Harford]

And I have your final challenge here for you. Well, of course, you've seen it already. It's from loyal listener Jonathan Trigell, and he's been looking at the Bible. In particular, he's interested in the lineage of Jesus. The Bible says Jesus was in the line of King David, which is important because the Messiah was expected to be of royal descent. But the Bible also has this to say about David's son, Solomon. King Solomon, however, loved many foreign women besides Pharaoh's daughter. Moabites, Ammonites, Edomites, Sidonians, and Hittites. Solomon held fast to them in love. He had 700 wives of royal birth and 300 concubines. And his wives led him astray. Well, under the circumstances, I suppose it is a risk that somebody leads someone astray. Anyway, Jonathan's question is this. If Solomon had about a thousand wives and concubines, and assuming he fathered children with many of them, wouldn't it be the case that by the time of Jesus, many generations later, pretty much everyone in Israel could claim to be a descendant of King David? Not our usual more or less fair, Jan, but what did you make of it?

[Yan Wong]

I love this question because you've chosen something for me which is right in my area of expertise, genetics and genealogy. And this actually has quite a lot of importance for people studying DNA and stuff like this, because that's how DNA is inherited through your family tree. The thing I think we should first say is that there's a massive difference between just following the male line, which is what's purported to happen to the biblical ancestry of Jesus. I'm following both the male and female and all the sort of combinations of those sort of lines. The easiest thing is to imagine it backwards in time. Actually, people do that. So you take yourself, or maybe everyone in Israel, and you go backwards. Now, if you look at yourself, well, you have only one father, one paternal grandfather, one paternal great grandfather, and so on. But if you take both sides, you have 2, 4, 8, 16. It increases exponentially.

[Tim Harford]

I've got four grandparents, eight great grandparents.

[Chris Giles]

Yeah, yeah.

[Yan Wong]

And it doesn't. There's this thing called the genealogical paradox, which means that by the time you get, say, 40 generations back, 2 to the 40 is 1 trillion, about more than the total population of the world. So there's this sort of paradox.

[Tim Harford]

There aren't enough great, great, great, great grandparents to go around.

[Yan Wong]

No, indeed. And the resolution to that is that the ancestors are sort of duplicates of each Other, you can go multiple routes through the family tree and hit one person through many different routes. And like any of these exponential things, the number of generations is absolutely crucial. And so we really want to find out. The number of generations between Jesus and David turns out to be about a thousand years. We're probably talking about 35 generations in total. Two to the 35 is 34 billion. We're talking a lot of potential.

[Tim Harford]

Jesus had 34 billion potential ancestors.

[Yan Wong]

Indeed.

[Tim Harford]

But some of them were duplicates.

[Yan Wong]

Yeah. There's so many ancestors, it's not very surprising that there's going to be overlap. If you go backwards in time, you take anyone in the population in Jesus's time, you go back only, in fact, you can calculate this, probably about 20 generations, they will share at least one of those ancestors, because there's so many. And in fact, you don't need to go much further before they share all their ancestors.

[Daniel Tammet]

Right.

[Yan Wong]

So you only need to go back about, as it happens, 35 generations for a population of about a million people, which is the population of Israel, about the time before. Everyone has all the same common ancestors. And in fact, those common ancestors represent about 80% of the population. So only 20% of people don't leave any descendants at all. Otherwise everyone in Israel is related to them directly after 35 generations.

[Tim Harford]

So we have the answer to Jonathan's question. In the time of Jesus, everybody, are we saying everyone was the.

[Yan Wong]

Yep, Everybody. Everybody in Israel.

[Tim Harford]

So we're saying everybody. We're not saying they all had the same ancestors.

[Yan Wong]

Yep, all the same ancestors. If you go back to the time when David was around, you take everyone in Israel at the time of Jesus, trace their ancestors back to when it was David. They're all the same.

[Tim Harford]

I didn't get enough sleep last night.

[Yan Wong]

And it's not just David, it's 80% of the population.

[Wesley Stevenson]

Yes.

[Tim Harford]

Looking back at Jonathan's question. So he's asking whether pretty much everyone in Israel could claim to be a descent of David. And you're saying yes, everyone in Israel could, and not just David, but in

[Yan Wong]

fact, and not just David. If you trace everyone back in Israel at the time of Jesus to 35 generations Previous to that, then they would share all their ancestors in common, which would be about 80% of the total population of Israel at the time, including David and David's manservant and David's barber. And all those people would probably be your ancestor if you were.

[Tim Harford]

And the other 20%, they didn't leave

[Yan Wong]

children or their children didn't leave children.

[Tim Harford]

Yan Wong, Never wrong. We hope you're listening to More or less in association with the Open University. Earlier this month, the sun came out

[Charlotte Macdonald]

with this official casualties soaring in 20 mph zones. Controversial 20 mph speed limits designed to cut road casualties are not working.

[Tim Harford]

Soon after, the story gathered momentum and it was picked up all over the place. Official figures suggest that the number of people killed or injured on roads with 20 mile an hour speed limits increased by almost a quarter last year. Councils have been given power. We've received more emails about this story than any other this series, all from listeners who find it hard to swallow. So, Charlotte MacDonald's here. Charlotte, can you bring truth and light?

[Charlotte Macdonald]

Well, there's one thing about this story that's true. Casualties on roads with 20 mile per hour speed limit to did increase between 2010 and 2011, as you heard Peter Donaldson say. These data came from the Department for Transport and were published almost a month and a half ago. One number reported by BBC online is that there has been a 17% increase in the total number of deaths on 20 mile per hour roads. But look at the absolute numbers on 20 mile per hour roads across the entire country. There were six deaths in 2010 and seven deaths in 2011.

[Tim Harford]

OK, so it's just not very useful to report that as a 17% increase. We have these rare tragedies. We'd hope to reduce their number over time, but it's just nonsense to suggest that a jump from six deaths to seven deaths is actually going to tell us anything.

[Charlotte Macdonald]

Exactly. If you look at injuries as well as deaths on 20 mile per hour roads, the total rose 24% to about 2,250.

[Tim Harford]

Now that sounds like a much more convincing increase. But look, this whole thing is the faux ness balonus. When I drive around, I notice a lot of 20 mile per hour signs where a few years ago I hardly saw any. And they seem to be suddenly in fashion amongst traffic planners. If there are a lot more 20 mph roads, then of course there are a lot more opportunities to have accidents on them.

[Charlotte Macdonald]

Yes, exactly. In an ideal world, we'd identify a bunch of roads as candidates for 20 mph zoning and then randomise putting up signs in some and leaving others the way they were to find out for sure whether the 20 mile per hour signs made a difference.

[Tim Harford]

But failing that, it would at least be nice to know how many more roads There are with 20mph speed limits and how many people use them. Doesn't the Department of Transport know?

[Charlotte Macdonald]

Not a clue. But we do Know that the government has been making it easier over the last few years for local councils to change speed limits on their roads, and a number of councils have done so. One of those is Bristol. In 2009, the city had fewer than 50 roads with a speed limit of 20 miles per hour and only 11 casualties reported on them that year. But during 2010, the council launched two pilots, one in May and one in October, lowering the speed limit to 20 miles per hour for around 500 roads.

[Tim Harford]

And did the number of casualties on 20 miles per hour roads go up?

[Charlotte Macdonald]

Yes. In 2010, there were 55 road casualties recorded on 20 mile per hour roads. And in 2011, there was a huge increase to 145.

[Tim Harford]

So, just thinking out loud, the number of 20 mile an hour roads increased roughly tenfold over two years and the number of accidents on them also increased roughly tenfold.

[Wesley Stevenson]

Yes.

[Charlotte Macdonald]

Ok, so you did that mental arithmetic, but there is a lot of things about those roads that you don't know. How long they are, how busy they are.

[Tim Harford]

Fine. But if there are more 20 mile per hour roads, it would hardly be a surprise or a problem to find that a higher proportion of accidents started happening on those roads. I am curious, though, Charlotte, do we have any real evidence about what 20 mile per hour roads do for road safety?

[Charlotte Macdonald]

Well, I spoke to Dr. Angela Raffle, consultant in Public health in Bristol. She helped Bristol Council launch its pilot.

[Angela Raffle]

What we've seen in Bristol is in our two pilot areas, we've evaluated them quite carefully. They were signs only, so no speed bumps. We've seen average speeds drop. That's really important. We've seen walking and cycling go up. We've seen support for it amongst local residents increase. 82% of people who live in the pilots think they're a really good idea. And we've seen no change at all in reliability and journey times for buses.

[Tim Harford]

Well, that sounds like positive stuff. We know in absolute terms the casualty numbers on these roads are going up because they have more roads. Do they think that these 20 mile an hour limits are actually bringing down casualty figures overall?

[Charlotte Macdonald]

Here's what she told me.

[Angela Raffle]

We cannot learn anything yet from Bristol's pilot on whether it has anything to do with casualties, because the numbers are tiny. They're, in a statistician's terminology, they're random, rare events. But there was a very detailed study from London, published in the British Medical Journal, which looked very carefully at statistics from 20 NPH zones. They found a reduction in severity of casualties.

[Charlotte Macdonald]

Now, that research also found that there was a reduction in road casualties in those zones in London. And we also know that faster cars do a lot more damage and take a lot longer to stop.

[Tim Harford]

Well, thank you, Charlotte. Before you go, how's your Olympic medal table looking now the Games are over,

[Charlotte Macdonald]

we created a table of Olympic medal projections based on how many medals we would expect each country to win based only on its population and GDP per capita. If you go to our website, BBC.co.ukmoreorless you'll find our analysis of the final medal table. But in a nutshell, well, big overachievers include Team gb, China, the us, Jamaica and Australia.

[Tim Harford]

Australia. The Australians don't believe that, but okay.

[Charlotte Macdonald]

And the underachievers, big underachievers are India, Brazil, Indonesia, Pakistan and Nigeria.

[Tim Harford]

Thanks, Charlotte. This week we heard that the rpi, the retail price index, a measure of inflation, has risen by 3.2%, which is more than expected. But here's the thought. What if the RPI number is tosh? Chris Giles, the Financial Times Economics editor, spends most of his working day reporting on Trumpetonshire. But he sometimes looks at the UK economy too, and he's exposed a weird flaw in the rpi, which seems a little dry and technical, but turns out to be much more important than you might think.

[Chris Giles]

The story is one of those interesting stories of unforeseen consequences. About three years ago, the Office for National Statistics realized that its sample size, when it sent out its people to go and collect prices for clothing around the country was getting too small because they were saying to the people who collect the prices that you have to be absolutely specific on the type of clothing that they had to go and collect. So let's say it was a shirt. They had to say it was a white shirt with a button cuffs and button down collars and a top pocket. And if the shirt didn't entirely match the description, then they wouldn't be able to collect the price. And they found that they had lots of gaps in their series which they thought was making the inflation series slightly suspect. So they relaxed the rules and said, you know these shirts, a white shirt is a white shirt and that can be essentially comparable. And they did really increase the number of price quotes they got.

[Tim Harford]

Now, this really doesn't sound like a big deal, but then something very odd started to happen and you could see it in the gap between the RPI, which had been tweaked, and an alternative measure of inflation called the CPI.

[Chris Giles]

In July 2011, we had a situation where based on the same price quotes in the same shops on the same day RPI clothing price inflation was about 12% and CPI clothing price inflation was 2%, a 10 percentage point difference.

[Tim Harford]

So what's going on? How can one measure of inflation be six times higher than another when the data going into the calculation is exactly the same? This problem goes back to the mid 18th century when Count Carly, a Venetian nobleman and financial expert, developed a way of measuring inflation now called the Carly Index. The Carly Index has been ditched by most advanced economists, but we still use it in the UK when we calculate parts of the retail price index. Here's the odd thing about the Carly Index. Imagine that your basket of goods contains two items, a shirt and a blouse. Last year a shirt cost £20 and a blouse cost £25. This year the shirt price has risen to £25 and the blouse price has fallen to £20. You might think that not much has changed. But the KALI index averages a 25% price rise for the shirt and a 20% price fall for the blouse and concludes that prices rose 2.5%. And what's worse, imagine that next year the shirt falls back to £20 and the blouse rises to its original price of £25. Now everything costs exactly what it did two years ago. But the Carley index says inflation was 2.5% in each year.

[Chris Giles]

The key property which is really problematic in the RPI in the way when you just take the average, the changes in prices, is that if prices rise and then they fall back to where they were, you would expect over the total period inflation to be zero. But actually that way of doing it doesn't give zero, it gives a positive number always because it's biased upwards.

[Tim Harford]

Carly Index has always had this quirk. But the unexpected side effect of getting all those extra price quotes for clothes was dramatically to increase its effect. This wouldn't matter except that many prices and wages are automatically linked to the rpi. The price for train tickets is linked to rpi, benefits used to be linked to RPI and the state pension still is. Under some circumstances, wage negotiations between employers and trade unions often use RPI as a starting point. If RPI is systematically overestimating inflation, it means rail passengers are systematically paying more than the rail regulator intended, benefit payments are or were systematically higher than the government intended, and so on. Over time, the mistakes can build up into serious money. And all because of some dodgy old maths from 18th century Venice. But look on the bright side.

[Chris Giles]

Well, there's some really good news because our main living standard measure, when we look at how much incomes household incomes have Risen has always been deflated or adjusted for inflation using the rpi. And so when we look back and say, oh, well, actually since 2002, incomes haven't grown very much. Well, they've actually grown considerably more than we thought by half a percentage point a year and more, even more recently. So the good news is that actually life has got better, although we probably banked all that. So it doesn't feel great just to be told it after the fact.

[Tim Harford]

Chris Giles of the Financial Times on More or less we think numbers help to understand the real world, but for Daniel Tammet, they're a lot more important than that. For him, numbers don't just help him to understand the real world, they're his ticket to being part of it. I've been talking to Daniel about his new book, Thinking in Numbers, and I asked him first to explain how he'd managed to learn Icelandic in one week.

[Daniel Tammet]

It goes back in part to the way that my mind, I guess, evolved as a young child. I had a very withdrawn, very awkward childhood, and we didn't have a name for it at the time. My parents came up with all kinds of names, hypersensitive, and my dad, in his typically colorful way, called me cac handed. I was very useless with everything that was the slightest bit practical. And in fact, the word that they were looking for didn't exist at the time was high functioning autistic savant syndrome. It's a bit of a mouthful, it's true, and it just means that my brain evolved a little bit differently. The connections have gone to different parts of the brain that maybe other brains don't have, don't those connections don't reach into those parts of the brain. And it gave me certain handicaps that I've had to work extremely hard to overcome, such as this conversation we're having now wouldn't have been possible for me quite a few years ago. I've learned to acquire those social skills and to find a way of putting feet in both worlds. The world of numbers and the world of people, world of language and books.

[Tim Harford]

And nearly a decade ago you stood in the Museum of the History of Science in Oxford and recited PI to how many digits was it?

[Daniel Tammet]

It was 22,514 decimal place took five hours and nine minutes. I describe PI as a poem because for me, the colors and the shapes that I experience when I think in this number and describe it as a landscape full of life, full of beauty.

[Tim Harford]

This is a book about, in part about your relationship with numbers. So I was expecting to read all these extraordinary tales that I couldn't relate to. But actually, in many ways, the anecdotes that you recall, the stories you tell, they're really stories of just a child who's curious about the world and curious about numbers. I remember doing at least one of the things you described doing. So perhaps many children have some kind of facility with numbers and a natural curiosity with numbers. And I wonder whether you feel that the adult world, our educational institutions, are terribly good at tapping into that.

[Daniel Tammet]

Absolutely. I mean, mathematics has meant so much to me because it has given me a way of smuggling my way into the world of people. Numbers are everywhere. They describe patterns that unify the world and makes it what it is. And so often in class, we lose that sense of mathematics as a universal subject that speaks to every part of human experience. My own experience of teaching, which was with children who were terrified of mathematics, as many children are, I realized that they actually had a pretty good understanding of numbers. And it was really just a case of appealing to their imaginations. And children have wonderful imaginations and schools seem to do so much to work the imagination out of them. And we need to show that mathematics is all about imagination. It's the science of imagination.

[Tim Harford]

Daniel Tammet, author of Thinking In Numbers, which is next week's book of the week here on Radio 4. And that's all we've got. Time for another programme. And another series draws to a close. It's sad, of course, but just think of all the fascinating things we've learned. Why shares are traded faster than ever while Tour de France cyclists are getting slower. We've unpicked dubious numbers, from Libor to homelessness to starving British children. We've proved that US presidents mums outlived those of British prime ministers and found the most dangerous place in crime drama. But more important than all that, we finally made our peace with Dibble. Even if I can't wholeheartedly endorse his new career in the glamour business. If you can't wait for the next series, do Visit our website, BBC.co.uk morealls and if you subscribe to our download, you'll hear the programmes we make year round for the World Service. Do also, please keep your ideas coming in to more or lessbc.co.uk. we'll be back in November. Until then, goodbye.

[Charlotte Macdonald]

More or Less was presented by Tim Harford, the Financial Times undercover Economist. The producer is Richard Knight. More or Less is made in association with the Open University.