Cameron’s 1000 jobs

Summary

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More or Less: Cameron’s 1000 Jobs

Host: Tim Harford (BBC Radio 4)
Episode Date: January 30, 2015
Episode Theme:
The episode explores how statistics are used (and sometimes misused) in political debates and everyday issues. This week’s topics include David Cameron's jobs claim, context for employment statistics, the true economics of dairy farming, the mathematics of love (and spreadsheets), the odds around birth due dates, teen pregnancy rates, and income comparisons.

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Main Discussion: Cameron’s "1000 Jobs a Day" Claim

Overview:
The episode opens with listener Nicola questioning then-Prime Minister David Cameron's claim that the Conservatives created "a thousand jobs for every day we've been in office" since 2010. Tim Harford and reporter Hannah Moore examine the truth and context of this statistic.

Key Points and Insights:

• Is the claim true?
  • Yes, in pure numbers: Since June 2010, jobs grew from 31.5 million to 33.5 million in the UK, equaling about 1,200 new jobs per day ([01:29]).
• Does that mean the government ‘created’ those jobs?
  • Not necessarily. Moore notes:

    "It's true I did start this job within the past five years, but I don't really think the government created it as such." ([00:58], Hannah Moore)

• Statistical context – is 1,000 jobs a day impressive?
  • Harford challenges:

    "There are more than 30 million jobs in the country ... is a thousand jobs a day a big number, a small number? It's just confusing." ([02:06], Tim Harford)

• Historical context:
  • Under Gordon Brown (2007-2010): 555,000 fewer jobs; about 500 jobs lost per day ([02:25]).
  • Under Tony Blair (1997-2007): just under 900 jobs/day created ([02:49]).
• Caveats:
  • Many new jobs are part-time or lower-paid; wage growth has not matched job growth.
  • The Institute for Fiscal Studies found median wages in 2014 were almost 5% lower than before the 2008 recession ([03:22]).

    "We haven't seen that wage growth for the labour force as a whole. So that suggests that the new jobs aren't paying as well as we'd hope." ([03:52], Tim Harford)

• Labour’s criticism:
  • Many more people want to work more hours, and wage stagnation supports critiques that these aren’t “the jobs we want.”

Notable Quote:

"Median hourly wages, adjusted for inflation, were still almost 5% lower in 2014 than in 2008. ... The fall was higher for better paid workers." ([03:22], Tim Harford)

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Segment: Interpreting “Unhappiest Workers” Headlines

Context:
A Guardian headline claimed UK nurses and teachers are among the “unhappiest” professions.

Key Insights:

• Survey source: 51% of nurses/health workers and 50% of teachers dissatisfied with pay.
• However, 52% of all UK workers are unhappy with their pay—making nurses and teachers actually less dissatisfied than average ([04:24]).

  "[These findings] make teachers and nurses … among the most dissatisfied … while also being more satisfied than the typical worker. Well done, the Guardian." ([04:24], Tim Harford)

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Correction Segment: UK Sex Industry and EU Accounts

Context:
A past episode discussed the estimation of the UK sex industry’s size for national accounts.

Key Points:

• Previous speculation was that prostitution accounted for 5% of the UK's EU bill.
• The Office for National Statistics (ONS) corrected this, saying the real effect was negligible ([05:55]).

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Segment: Are Dairy Farmers Paid Less Than the Cost of Milk?

Listener Question:
Val Hamilton asks if dairy farmers really make a loss on every litre of milk produced.

Key Insights:

• The National Farmers Union estimates average production cost at 28 pence/litre.
• Supermarkets’ prices to farmers:
  • Sainsbury’s & M&S: 34p/litre
  • Tesco: 32p/litre
  • Co-op: 30.5p/litre ([08:29], Charlotte Smith)
• But most milk is sold to processors offering 22–25p/litre—below the average cost ([08:45], [09:07]).

  "Those farmers aren't getting anything like the average of 28 pence a litre. It's costing them." ([09:27], Charlotte Smith)

• The milk market is volatile, with global surpluses and political factors (like the Russian import ban) affecting prices ([09:56]).
• Fewer dairy farmers now, but stable production volumes ([10:30]).
• Direct subsidies usually calculated by land area, not milk production ([10:40]).
• Cultural importance: milk is a daily necessity and part of Britain’s rural imagery ([11:14]).
• Bottom line: Some farmers are paid under cost, others over—it “depends” ([11:57]).

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Segment: The Mathematics of Finding Love ("Optimal Stopping Problem")

Guest: Matt Parker, mathematician and comedian

Key Points:

• “Optimal stopping problem” offers a formula to maximize your odds of choosing the best life partner:

  "You need to look at the total number of people you will date … calculate the square root ... then go through that first set, automatically reject them, then pick the next person as good or better..." ([15:08], Matt Parker)

• Many practical limitations: unrealistic assumptions, no allowance for change, limited real applicability.

  “A mathematical model is only as good as the starting assumptions … I wouldn't recommend living life, you know, following this down to the algorithm.” ([17:44], Matt Parker)

• Fun but flawed as a real-life algorithm; people often settle too soon or survey endlessly ([18:00]).

Memorable Moment:
Parker jokes:

“I am a man of many spreadsheets. In fact, I have a spreadsheet to keep track of my top favourite spreadsheets.” ([18:41], Matt Parker)

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Segment: Probability of Friends Giving Birth on the Same Day

Listener Question:
Penelope and her friend Eleanor are both expecting babies with the same due date (April 4th). What are the chances they’ll give birth on the same day?

Key Insights:

• Due dates now set by ultrasound, not counting days from last period ([20:26], Professor Jason Gardosi).
• Only about 4% of babies are born on their estimated due date ([21:17]).
• Probability of both babies being born on the due date: ~1 in 500 ([21:28]).
• Wider window: 94% born within two weeks of the estimate; about 1 in 30 chance both are born on the same day within that range ([23:14]).

  “Now, there's almost no chance that Penelope and Eleanor will both have their babies on the 4th of April. ... But ... two full-term babies with the same estimated date ... being born on the same date?... It’s one in 30.” ([23:14], Tim Harford)

• The “due date” is a helpful clinical benchmark, not a consumer expectation ([23:25], Prof. Gardosi).

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Segment: Stats on Teenage Pregnancy

Context:
Reference to a New York Times piece claiming a third of US girls become pregnant as teens.

Key Points:

• The 1-in-3 figure came from US data in 2006, tracking risk of at least one teen pregnancy per girl, not number of births ([24:10]).
• Recent data (2010): closer to 1-in-4 US girls; the teen birth rate is falling ([25:05]).

  “Unless ... a big rise in abortions, ... the rate ... could have gone down to 1 in 5.” ([25:31], Tim Harford)

• The US rate, while falling, is still higher than most developed countries, including the UK ([25:46]).
• England and Wales have the highest rates in Western Europe, though figures are coming down. More comprehensive sex education and accessible services in Northern/Western Europe are cited as reasons for lower rates there ([26:14], Prof. Roger Ingham).

  "Sex education ... is much, much more advanced ... start much earlier talking about relationships, respect, mutuality and consent ..." ([26:14], Prof. Ingham)

• The decline in the US varies by state despite different educational policies, so other factors likely contribute ([26:50]).

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Memorable Quotes & Moments

• "All politicians like to claim credit for everything good that's happened during their tenure." ([01:05], Tim Harford)
• "It's just confusing." ([02:06], Tim Harford on the 'jobs per day' stat)
• "Naught out of 10 for tact, but 10 out of 10 for fact." ([14:09], Tim Harford on Stuart Broad's global income tweet)
• "If all dairy farmers lose money all the time, then surely every dairy farm in the country would have left the business by now." ([06:52], Tim Harford)
• "I am a man of many spreadsheets." ([18:41], Matt Parker)

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Useful Timestamps

• Jobs claim examined: 00:23–03:52
• Wages and job quality: 03:01–03:52
• Unhappy workers headlines: 04:19–05:04
• ONS Sex Industry correction: 05:04–06:29
• Dairy farming economics: 06:29–12:01
• Mathematics of dating/love: 15:08–18:48
• Friends and birth date odds: 19:09–23:25
• Teen pregnancy US & UK: 24:10–27:07

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Summary Takeaways

• Cameron’s ‘jobs per day’ claim is numerically true, but misses vital context about wage quality and economic starting points.
• Teachers and nurses are dissatisfied with pay, but less so than the average UK worker—a cautionary tale about misleading statistics.
• Many UK dairy farmers currently sell milk at a loss, though the specifics vary based on their purchasers and circumstances.
• Mathematical strategies offer fun (if imperfect) approaches to life choices—be it dating or spreadsheet management.
• The ‘due date’ for babies is only a rough guide—shared due dates are seldom matched by actual shared birthdays.
• US teen pregnancy rates are dropping fast, but the rate is still high comparatively; figures depend on statistical definitions and social policy context.

Original episode tone: dry wit, accessible statistical explanations, occasional playful banter. Nothing escapes scrutiny!

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Transcript

[A]

Thank you for downloading this program from BBC Radio 4. I'm Tim Harford. Hello and welcome to More Or Less, the programme which can turn around even the most suspect of statistics this week, dating milk, babies and spreadsheets.

[B]

I am a man of many spreadsheets. In fact, I have a spreadsheet to keep track of my top favourite spreadsheets.

[A]

But first, let's talk about jobs. Loyal listener Nicola emailed us this week at more or lessbc.co.uk I heard David

[C]

Cameron's claim on the Radio 4's Today programme this morning that the Conservatives have

[A]

created a thousand jobs for every day we've been in office. I am a 54 year old middle

[D]

class woman living in rural Bedfordshire and

[C]

even I was driven to shout at the radio. Which one of us is right, please?

[A]

Well, thank you for your question, Nicola, and here to help me answer it is one of those lucky people with one of Mr. Cameron's new jobs, our cub reporter, Hannah Moore.

[D]

Well, it's true I did start this job within the past five years, but I don't really think the government created it as such.

[A]

Hannah, we've got to play by the rules. All politicians like to claim credit for everything good that's happened during their tenure. So say thank you to the Prime Minister for your job.

[D]

Thank you wasn't really up to him.

[A]

So, leaving aside the question of whether the government is responsible for creating these jobs, is the number true? Have a thousand jobs a day been created since the coalition government came to power?

[D]

In short, yes. There were 31 and a half million jobs in this country when David Cameron came into power and there are 33 and a half million now. So that's just over 2 million more jobs now than in June 2010. That equates to almost 1,200 more jobs per day.

[A]

Well, I must confess that I was annoyed by Mr. Cameron's statistical boast myself. And that wasn't because I thought it wasn't true. I assumed it probably was, but it was because it's really unhelpful. I mean, there are more than 30 million jobs in the country. As you said, there are 365 days in a year. So is a thousand jobs a day a big number, a small number?

[E]

What?

[A]

It's just confusing.

[D]

So I wanted to put the number into context and one way to do that is to look at how many jobs a day were created under Gordon Brown's government and Tony Blair's government.

[A]

Well, I think we know that Gordon Brown didn't do too well on that Score. He was only Prime Minister for three years and Northern Rock went belly up just a few months after he started.

[D]

Yes, there were 555,000 fewer jobs in the country at the end of his premiership. So that's 500 jobs destroyed per day.

[A]

Yauch. And that presumably is one reason why David Cameron's job creation record is pretty good. He started from such a low point. But what about Tony Blair? I mean, whether by good luck or good leadership, he presided over a long economic boom.

[D]

Yes, but just under 900 jobs a day were created while Tony Blair was prime minister between 1997 and 2007, well below David Cameron's nearly 1,200.

[A]

Well, well, now I think we know what Labour would say about this. Yes, there may be jobs, but they're not the jobs we want.

[D]

And they would have a point. There are far more people in part time work who say they want to work more hours, for example, than before the crisis. And the picture on wages squares firmly with the Labour Party's criticism.

[A]

The Institute for Fiscal Studies has just published a report on this and it found that median hourly wages, adjusted for inflation, were still almost 5% lower in 2014 than in 2008. Just before the recession. Median weekly wages were down even more. And by the way, the fall was higher for better paid workers.

[D]

Now, is that fall because wages are stagnant in the jobs that people already have, or is it because all these new jobs pay badly and are pulling down the median?

[A]

It's the latter, Hannah. People who've had the same full time job all along have seen their real pay rising for the past four years. That's on average, of course, but we haven't seen that wage growth for the labour force as a whole. So that suggests that the new jobs aren't paying as well as we'd hope. Thank you, Hannah. There was nary a job stat that escaped our notice this week. We spotted a headline in the Guardian on Monday that just didn't ring True.

[B]

The UK's unhappiest workers, retail staff, nurses and teachers.

[A]

But are teachers and nurses really that unhappy with their jobs? 51% of nurses and healthcare workers and 50% of teachers said they were dissatisfied with their pay. But this made them, according to the Guardian, among the unhappiest professions in the country. But the very same survey found that 52% of workers in general were unhappy with their pay, which makes teachers and nurses simultaneously among the most dissatisfied workers in the country, while also being more satisfied than the typical worker. Well done, the Guardian. You're Listening to more or less. And Ruth Alexander's joining me. What have you got for us, Ruth?

[C]

Since we like everyone to get their numbers right, including ourselves, it's time for a correction. You may remember that last year the Office for National Statistics produced an estimate of the size of the sex industry in the uk, part of a standardisation of national accounts across the European Union. Well, in the very first programme of this series, Professor Sir David Spiegelhalter joined us to explain why he thought the ONS numbers didn't really add up. The ONS complained about what he said. Here's a little clip.

[A]

The crucial thing is this assumption that

[E]

each person working is seeing 1200 clients a year. And this seems very high indeed.

[A]

And we can do a few little reality checks on this. It would mean, for example, that everybody

[E]

working in prostitution was actually turning over £100,000 a year.

[A]

And this doesn't seem plausible from people who know about these things.

[C]

We, like the Guardian and the Telegraph, explained that these ONS estimates had contributed to the additional demand for payment that the EU had handed to the UK government. Our calculation suggested prostitution might have been responsible for 5% of the bill. But the ONS argues that that isn't right and that these changes had a negligible influence on the side of the bill from the eu. So, apolog to the Office for National Statistics, we did ask the ONSK if someone would like to come on air to discuss David Spiegelhalter's critique of their numbers. They weren't so keen on that. Very wise.

[A]

Well, thank you very much, Ruth. Loyal listener Val Hamilton has been in touch to.

[F]

Could you look into the regularly repeated

[C]

fact that dairy farmers make a loss

[F]

on each litre of milk that they produce?

[C]

I'm originally from a farming community, so do have sympathy with farmers, but I do wonder if this takes into account the subsidies received in the single payment, for example.

[A]

I have sympathy too. I used to go out with a dairy farmer's daughter. But, yeah, it's a fair question, Val. If all dairy farmers lose money all the time, then surely every dairy farm in the country would have left the business by now. So we turned for clarity to our colleagues at Farming Today. They told us that the standard number for the cost of milk comes from an estimate by the National Farmers Union, which says it's 28 pence a litre. But the actual cost of production varies a great deal, depending on the type of farm, the land and how remote the farm is. So with that average of 28 pence a litre in mind, one of farming. Today's presenters, Charlotte Smith came to More or Less Towers to tell us what farmers are paid for their milk.

[G]

How much you are paid depends on who you're selling it to and what it's going to be used for. About half the milk produced in the UK goes as liquid milk. The rest goes into food like cheese and yogurt and so on and so forth.

[A]

Cheese, lovely.

[G]

Forget cheese just for a minute, okay? Of that liquid milk, that's half the milk produced in the uk. A third of it is sold to retailers who base the price they pay on what it costs the farmers to produce milk. So that's people. Tesco, Sainsbury's, Ms. And the Co Op, they all have dedicated suppliers.

[A]

So there's this sort of risk sharing agreement. You know, when the cost goes up, the supermarkets will pay a bit more and when the cost goes down, the supermarkets will pay a bit less. Have I understood that right?

[G]

Yes. In simple terms, yes.

[A]

And that's because they want these long term relationships with the suppliers.

[G]

Exactly. Because they need milk. And so Ms. And Sainsbury's at the moment are paying 34 pence a litre, Tesco 32 pence a litre, the CO OP 30 and a half pence a litre.

[A]

Those numbers, if I'm right, those are all a little bit more than the, than the average cost. The National Farmers Union quote the rest

[G]

of the milk that is sold to processors and those are the people who have over the past year been making big cuts. Now Arla announced just recently that for February its price will stay the same at 25 pence a litre. Muller Weizman also holding prices at 25 pence a litre. Dairycrest says next month there will be a further cut and so farmers supplying them will get about 24 and a half pence a litre. And First Milk, which is a farmer cooperative which announced delays in payments recently, is paying about 22 pence a litre to its producers. So there you can see that those farmers aren't getting anything like the average of 28 pence a litre. It's costing them.

[A]

And to come back to my favourite subject of cheese. So I mean, is the milk that goes into cheese, is that kind of. Yeah, that's where all the money gets made, you know, or the super high markups. Or is that where, you know, you dump the milk you can't get rid of. It goes into cheese. But if only.

[G]

Yes to all of the above. It depends, it depends, it depends, it depends. Globally it has been a good time for milk. So there is a Lot more milk being produced, which is potentially a bad

[A]

time for milk farmers because it puts downward pressure on prices.

[G]

Exactly. And what complicated it was that in China, which was a massively expanding market, they had a couple of scandals, so there wasn't so much demand. And at the same time, Russia announced an import ban. So a lot of the cheese and other milk products which would ordinarily go into Russia are now back on the world and particularly the European market.

[A]

How is the milk industry doing in the long run as far as employment's concerned and as far as production is concerned? Are we making more milk than we used to? Do we have more dairy farmers than we used to or we have fewer

[G]

dairy farmers, but milk production is relatively consistent.

[A]

What subsidies or other market regulations are influencing the production of milk now?

[G]

The cost of production is price per litre of milk. The basic farm payment subsidy now in the European Union is, isn't included in that calculation because it's paid based on the amount of land that you have and you may not be using on a typical farm all that land for your dairy business.

[A]

I do not remember hearing that rice farmers are being bullied by the supermarkets or that wheat farmers are being bullied by the supermarkets. It seems to be a specific story about milk. Why is it such a cultural touchstone?

[G]

I think it is partly that the vast majority of people use milk every day and I think it's also partly that as you drive down the motorway, you are used to seeing cows in fields, you are used to that countryside created by that type of farming. And so when farmers say, I am not going to do this anymore, I am either going to get out of the industry altogether or I am going to use the land and do something else. They are not just changing their business, they are changing your view and that touches us all.

[A]

So you've explained it all to us. It's clearly very simple. So is it true that British farmers are being paid less than the cost of production for their milk or not come off the fence?

[G]

Well, it depends. Yes, some are and no, some aren't.

[A]

I'll settle for that. Thank you very much, Charlotte Smith of BBC Radio 4's Farming Today. You're listening to More Or Less. You can email us your questions @more or lessbc now, our next guest is Matt Parker. That unusual combination of mathematician guys. What? What's going on?

[H]

Tim, sorry to interrupt, but somebody's bad mouthing the CPI out there. I thought you'd want to know.

[A]

The cpi, the cad. Let me grab my fighting slide. Ross, show them what For

[C]

Keith, what are you doing?

[H]

Oh, it's just one of these items about global income distribution. You know, the 1% inequality, yada, yada, yada. I know, Tim's fed up of them.

[C]

Oh, yeah, but this one's about. It's Stuart Broad, isn't it?

[H]

It is. The England cricketer managed to wind a few people up with a tweet this week. He I've heard if you earn minimum wage in England, you're in the top 10% earners in the world. Stayhumble.

[C]

Well, no doubt that was supposed to be some sort of profound reflection on the nature of his own good fortune,

[H]

but since Stewart himself reckons he made his first million pounds by the age of 23, his phrasing was a little clumsy. He's apologised since.

[C]

Well, tact and diplomacy be hanged, though, because many loyal listeners are keen to know, aren't they? Was Stewart, as a matter of fact, correct?

[H]

It's a good question. Let's turn to World bank policy research paper 6719. Yeah, we all know that one. It was published just over a year ago and one of the authors is Branko Milanovic, one of the most respected scholars of global income distribution. On page 25, I think you'll see that to be in the world's top 10% by income, you need to be

[C]

making, oh, yes, $15,000 or thereabouts. Now, it says here that the number is in $2005, though, so we need to tweak it to accommodate inflation.

[H]

It's about $18,000 in today's terms, or £12,000.

[C]

So if you work at the UK minimum wage of £6.50 an hour for 36 hours a week with paid holiday at the end of the year, you'll have earned 12,168 pounds, just enough to

[H]

place you into Branko Milanovic's top 10%.

[C]

So take a bow, Stuart Broad. Naught out of 10 for tact, but 10 out of 10 for fact. Did you catch them, Tim?

[A]

No, no, it's odd. They must have seen me coming. So, where were we? Ah, yes. Our next guest is Matt Parker, that unusual combination of mathematician and stand up comedian. He recently wrote a book called Things to make and do in the Fourth Dimension. It's a collection of tricks, games and puzzles that reveal bigger lessons about the world around us. Maths says Matt can even help you find the right life partner. Well, I laid myself down on his couch and I opened my heart. I'm pleased to say I'm happily married. But occasionally I have doubts as to whether maybe I settled down too soon. Could I have done better if I waited? Seems unlikely, but it's quite possible my wife could have done better if she had waited. So can maths help me?

[B]

I mean, these are very valid concerns and ones you should probably not broadcast on national radio. But there is a mathematical approach you could have taken. In fact, retrospectively, you could look back to see how you did and the problem you were faced, in fact, we're all faced with, is when you're looking for a life partner as you're interviewing people, or I believe dating is what it's commonly called as you're going through the candidates. If you meet a candidate and you assess their qualities and then you reject them later on, it's very hard to go back and say, look, I've changed my mind. It turns out you were the best I'm ever going to do. But on the flip side, if you settle down with someone straight away, you have no idea what the general quality of possible candidates was. So you're faced with a problem. You've got to interview or survey a certain number of possible candidates and reject them to get a sense of the quality. But you don't want to do that for too many, or you may pass by the best option. And so the question is, how many people do you reject to get a sense of the standard? And at what point do you stop rejecting and you start choosing? And that is called the optimal stopping problem. And mathematically, we know if you want to get the best person on average, you need to look at the total number of people you will date across your life. You then calculate the square root of that number of people. And so let's say you were going to date 100 people in your life. Your square root is 10. You then go through that first 10 people and you automatically reject them. But you keep track, I mean, maybe log them in a spreadsheet as to who was the best. And then once you've gone through that, you then keep dating people until you meet someone who is as good as or better than anyone you saw in your original sample as such, and that mathematically will give you the best result on average.

[A]

There are all sorts of assumptions that we're making with the optimal stopping problem. Not only the distribution of partners, but what counts as an interview or a date. How long do you need to date somebody before you can assess their quality? We're sort of assuming quality doesn't change. You don't change, your partner doesn't change. There's no role for divorce in this scenario. We're assuming that you know with certainty how many people you could possibly date over the course of your lifetime. We're assuming there's no such thing as being in a hurry, being impatient to settle down. So there are all sorts of tweaks we could make and they might totally change the answer. And so at the risk of being a killjoy, I have to say, well, what's the point of this if it's not going to give us an answer that really works in the real world? Why are we doing it at all?

[B]

You're absolutely correct. I mean, as always, a mathematical model is only as good as the starting assumptions, how many things you factor in and how accurate you are at factoring those in. And so I wouldn't recommend living life, you know, following this down to the algorith. You know, clinically locate the person you have then calculated to be your best partner. But it isn't a reasonably good guide. Research seems to show that people on average settle down too soon. And this is not just finding life partners. The same thing applies to buying a house, buying a secondhand car. And so as a guide, it can give you a better sense. And people tend to err on not sampling enough. But then on the flip side, online dating means a lot of people get in a cycle of never being able to stop surveying. They always think, well, maybe there's someone better out. And so you're right, you shouldn't religiously follow this algorithm. But it is a reasonable guide to show you roughly what you should be doing.

[A]

Do you have a spreadsheet, Matt?

[B]

I am a man of many spreadsheets. In fact, I have a spreadsheet to keep track of my top favorite spreadsheets.

[A]

Matt Parker. Now, when you found the one, it can lead to thoughts of babies. Adorable, beautiful, noisy babies. It certainly turned out that way for loyal listener Penelope Chaney, who's been in touch with a question.

[F]

I'm expecting a baby in April and discovered that one of my close friends is also expecting a baby on the same day.

[A]

That close friend is Eleanor Marshall, and the day in question is the 4th of April.

[F]

This led us to wonder what the probability was of these two children actually having the same birthday and whether, you know, obviously whether they'd be born on their due dates or different days. But what the chances were of those children who have started in a similar way actually having the same birthday in the long term?

[A]

Well, we don't know how similar a way they started. I don't even need to go into

[F]

that, but that's not what I meant.

[A]

I imagine the details are broadly the same, but. So thank you, Penelope. So, Eleanor, your friend, you're on the line as well. Did Penelope tell you she was emailing us about this?

[I]

No, she didn't.

[A]

Oh, how naughty.

[I]

But she told me once you had got in touch with her and expressed an interest in exploring this a little bit more. And to be honest, I'm quite intrigued myself to know what the odds are.

[A]

Well, so were we. Let's start with the question of how the expected date of delivery is calculated. We got on to Jason Gardosi of the Perinatal Institute who told us that it used to be done by adding 280 days to the date of a woman's last period. But that's a bit old fashioned.

[J]

That is old school, although still being practiced in many areas in many countries and is really the first step whereby you use the first day of the last menstrual period from which to then count the length of pregnancy.

[A]

Professor Gardozzi told me that studies had shown that dating through ultrasound by measuring the size of the foetus is actually a more accurate measure. Both Penelope and Eleanor's expected dates of delivery were calculated from their ultrasound scans. So that's a good start. Penelope already has one child and Eleanor has two. Both of their pregnancies this time around are straightforward and low risk. So given all this, how likely is it that women like them will deliver on the dates given to them?

[J]

Well, actually most babies are not born on the predicted or estimated date of delivery, but in fact only about 4%.

[A]

It's 4.4% to be precise. And that's for women who have a completely normal pregnancy. And that's using UK expected dates of delivery because these things are done differently all around the world. So the chances of our two expectant mothers both delivering on the 4th of April really don't look good. They're about 1 in 500 in fact. So is that disappointing?

[I]

I don't think it makes a huge difference. It's not like, you know, it's a wonderful coincidence, but it's not like we did it on purpose, hoping that they would share a birthday.

[A]

No, that would be weird.

[I]

It really would. We're not that close friends.

[A]

So if the estimated date of delivery is wrong so often, why do we even need it? Professor Gardozzi says it's a useful metric not for patients, but for doctors. Medical professionals use it as a benchmark to let them evaluate test results and judge how the baby's develop. If we set aside premature births and other problem pregnancies and focus only on normal pregnancies. The figures show that 94% of babies are born within two weeks of the estimated date of delivery. In the UK, they're actually marginally more likely to be born four days overdue than on the estimated date of delivery. Now, there's almost no chance that Penelope and Eleanor will both have their babies on the 4th of April. But what about the chance that, whether early or late, two full term babies with the same estimated date of delivery are in fact born on the same date? Give me a break. It's not that interesting. It's one in 30.

[F]

Wow. That's quite high then.

[I]

That is quite high.

[A]

There you go.

[J]

Are you pleased?

[F]

It's higher than I thought it would be.

[I]

Yeah, definitely.

[A]

So what should we take away from this? Professor Gardozzi doesn't like the term due date. It smacks of a deadline. His message for expectant mothers is that if your baby seems overdue, there's no reason to be anxious. There is no reason to expect a baby to pay attention to what is, after all, a fairly arbitrary metric. We'll make sure we catch up with Penelope and Eleanor in April, but in the meantime, I'm sure you'll join me in wishing them both luck. While we're on the subject of babies, another statistic caught our eye. It was in a New York Times opinion piece by Nicholas Christophe. He said that about one third of American girls become pregnant as teenagers. Now that seemed very high to us, didn't it, Ruth?

[C]

It did. And looking into it, we found that the 1 in 3 figure comes from the National Campaign to Prevent Teen and Unplanned Pregnancy, which is a non profit organization in the United States. And what they've done is calculate the cumulative risk of a teenager becoming pregnant once between the ages of 15 and 19. And they were using the data from 2006. And the thing is, the rate of teenage pregnancy has been falling sharply. It's fallen by half over the past two decades and that is truly one of the US great success stories, according to the programme director of the national campaign, Bill Albert, who we've been talking to.

[A]

Ok, so this pregnancy rate then, it's likely to be lower. Now, do we know the most up to date number?

[C]

We've had a look at this and we've used the same method, using the latest set of complete data, which is from 2010. And that puts the figure much lower. It suggests that one in four teenage girls in the US become pregnant that's

[A]

down from Nick Kristof's figure of one in three, but it still seems like quite a big number.

[C]

Well, some more recent data suggests it could already be even lower than that, though the US teenage birth rate for 2013 is about a fifth lower than it was three years earlier. We don't have abortion data, though. I must say that.

[A]

And that reminds me that we're not talking about the number of teenage mothers here, we're talking about teen pregnancies and some of them will end in abortion or in miscarriage.

[C]

That's right. But now to sum up, unless there has been a big rise in the number of abortions happening, we think the rate of American teenage girls becoming pregnant could have gone down to 1 in 5.

[A]

How does the American picture compare to the situation in the UK?

[C]

Well, while the US has far fewer teenagers getting pregnant than it did 20 years ago, as we were just discussing its, teenagers still have babies at a much higher rate than in other richer developed countries like the uk. We don't have pregnancy data for the uk, but we do know that the number of births have been going down in a similar way. However, Professor Roger Ingham from the University of Southampton, who advised the government for 12 years on its strategy to reduce teen pregnancy, says more could be done.

[E]

England and Wales certainly have the highest figures in Western Europe and have done for a number of years. Even though the numbers are coming down rapidly, they're still higher than the vast majority of other countries. The countries that have lower figures are the Netherlands, Scandinavian countries and Switzerland. There are various reasons why this is the case. One of them is that the sex education in these countries is much, much more advanced than it is in England. They start much earlier talking about relationships and about respect and about mutuality and consent, and they have services that are much more accessible by young people.

[C]

But while Roger Ingham thinks sex education is effective at reducing teen pregnancies, evidence from the United States suggests that can't be the whole story because there programs are different in every state and yet the decline in pregnancies has occurred across the whole country.

[A]

A puzzle. Well, thank you very much, Ruth. Ruth Alexander. That's all we have time for this week, but you can always download this or previous editions of the programme via BBC Co uk. More or Less. Please keep your comments and your questions coming in to More or [e-mail] until next week. Goodbye. And just a reminder that you can download more [e-mail] Radio 4.