Strokes, Teachers, Confused Computers 15 May15

Summary

Podcast Summary: More or Less – “Strokes, Teachers, Confused Computers” (15 May 2015)

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Main Theme

This episode of More or Less, hosted by Tim Harford, unpacks and critically assesses the use and misuse of statistics in recent news stories. The team tackles alarming claims about rising strokes in young people, exposes a widely reported myth about teacher dropout rates, explains how computers struggle with large numbers (with real-world consequences), and analyzes how the UK election outcome would differ under proportional representation.

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Episode Breakdown

1. Are Strokes Really Increasing in Working-Age People?

[00:58–05:13]

• Claim in News: Multiple reports claim a “sharp rise” in strokes among people in their 40s and 50s (Sam Friedman, Wesley Stevenson, Charlotte MacDonald, [00:58–01:13]).
  • Example statistic: Stroke Association says hospital admissions for men 40-54 for stroke have more than doubled; admissions for women up by a third.
• Data Source: Hospital admissions, per the Stroke Association.
• Skepticism: Tim Harford notes listeners questioned if incidence really is rising ([01:13]).
• Expert Analysis: Interview with Professor Tony Rudd, King’s College London and NHS Clinical Director of Stroke.
  • On Hospital Admission Data: The rise is likely due to practice changes, not a rise in underlying incidence ([02:07]):

    “We are admitting more patients with mini strokes to hospital than we ever used to… I think it’s probably more likely to be due to the fact that we’re just admitting a greater proportion of patients than we used to.” – Prof. Tony Rudd ([02:07])

  • Population Incidence: Two long-running studies (Oxford, South London) show overall stroke incidence is falling in all age groups ([02:47]):

    “What they show is that the overall incidence of stroke is falling quite markedly and that is in all age groups.” – Prof. Tony Rudd ([02:47])

  • On ‘Rocketed’ Claims: Data doesn’t support the “alarming increase” narrative ([03:20]):

    “No, I don’t think they are justified in saying that… It’s important that the data are used as carefully and as accurately as possible.” ([03:24])

  • On Lifestyle Risks: Rising diabetes and obesity are real concerns, but the data don’t yet show rising stroke incidence ([04:05]):

    “We do know that sedentary lifestyle…is happening as a background phenomenon… but I don’t think we’ve really got strong enough data to be able to absolutely say that’s happened yet.” ([04:05])

• Key Takeaway: Hospital admissions for stroke are up because of better awareness and diagnosis. Actual stroke incidence is down across all age groups. There is concern for the future due to rising diabetes, but it isn’t showing in data yet ([04:48–05:13]).

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2. The Myth of 40% of Teachers Quitting After One Year

[05:54–09:43]

• Headline Claim: “40% of teachers quit after one year.” – Multiple newspapers ([05:54])
• Is It True? Charlotte MacDonald: “This one is just wrong.” ([06:10])
• Clarification:
  • Actual Statistic: Only about 9% of new teachers in England leave after one year ([06:18–06:35]).

    “It’s 9%.” – Sam Friedman, Teach First ([06:20]) “Fewer than 1 in 10 teachers are leaving after a year.” – Tim Harford ([06:41])

  • Origins of the 40% Figure: Derived from a union speech referencing "just 62% of newly qualified teachers…were still in teaching a year later" ([06:49–07:10]).
    • This includes those who never start teaching, those going overseas, private sector, or other educational roles – so, not quitting in the sense suggested ([07:16]):

    “The Atlanta union included newly qualified teachers who haven’t got teaching jobs in the first place…” – Charlotte MacDonald ([07:16])

  • How Long Until 40% Quit? It takes 13 years before 38–40% of teachers leave the profession ([08:01]):

    “That would take 13 years. The majority of teachers stay in the job for well over a decade.” – Charlotte MacDonald ([08:01])

• Newspaper Correction: The Independent apologized for the misinterpretation and gets a “More or Less gold star” ([08:15]).
• Union Statement: Difficulty finding precise numbers acknowledged; statistics used “in good faith” ([08:26]).
• Teacher Morale: Cabinet Office study (though not transparent) suggests teachers among the most satisfied professionals ([08:42]).
• Key Issue: “Retention isn’t the big problem, it’s recruitment.” – Charlotte MacDonald ([09:06])
• Numbers Matter: “Numbers do really change the way people think about their careers…” – Sam Friedman ([09:10])
  • Cautions that such myths could deter future teachers ([09:10–09:43]).

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3. When Computers Can’t Count: The Trouble With Big Numbers

[10:00–16:38]

• Introduction: Tim tells the story of the Ariane 5 rocket explosion (1996) due to a computer integer overflow ([10:00–11:52]).
• Explanation by Chris Baranjuk (Science/Tech Journalist):
  • Software from Ariane 4 reused, but it made incorrect assumptions about allowable values. A number too big was sent to a storage space too small – triggered self-destruct ([11:12–11:52]).

    “There was a number in the software that was trying to be converted from a large space...into a much smaller one. And consequently that number didn't fit...and a self-destruct sequence was initiated.” – Chris Baranjuk ([11:12]) "37 seconds into its flight, it ended in a ball of fire. Expensive, very expensive…" ([11:54])

• Another Example: Boeing 787 aircraft counter maxes out after 248 days, can shut down engine power if not reset ([13:14–13:34]).
  • “If the counter does reach that maximum… it’ll enter a fail safe mode, shut down part of the engines…” ([13:34])
• Why Can’t Computers Just Handle Big Numbers? Efficient design makes tradeoffs about how big numbers need to be ([13:49–14:43]).
• The Millennium Bug (Y2K): Many early computers counted years with 2 digits, leading to panics/problems as the year 2000 approached ([14:43–15:06]).
  • Programmers worked hard to prevent issues; there were incidents (e.g. clocks showing year 1900, errors on websites) ([15:06]).
• Gangnam Style on YouTube: Video crashed YouTube’s view counter at 2,147,483,647 (the 32-bit integer limit), prompting an update ([15:06]):

  “When it reached a very specific number… it actually maxed out the number of views YouTube can record at that time. But YouTube then of course updated its software…” ([16:02])

• Takeaway: Integer overflow errors are surprisingly common, can have major real-world effects, but can be addressed if anticipated.

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4. Election Numbers: What If the UK Used Proportional Representation?

[16:38–22:00]

• Election Discontent: Protests following Conservative victory; their 37% of vote led to majority of seats. 2015 election was one of the least proportional in recent UK history ([16:38–17:27]).
• Disproportionate Results:
  • Conservatives: 34,000 votes per seat.
  • Labour: 40,000 votes per seat.
  • SNP: 26,000.
  • Greens: >1 million per seat. UKIP: ~4 million per seat ([18:25]).
• Re-calculating by Proportional Representation (PR):
  • Projected PR Seat Distribution ([18:54–19:45])
    • Conservatives: 242
    • Labour: 199
    • Lib Dems: 51 (versus 8)
    • UKIP: 82 (versus 1)
    • SNP: 31 (versus actual 56)
    • Plaid Cymru: 3
    • Greens: 24 (versus 1)

    “A very different result then…” – Tim Harford ([19:45])

• Outcome: Conservatives still largest party, but would likely need a coalition with UKIP to govern ([20:09–20:22]).
• Other Systems: Alternative Vote (AV) system could yield slightly different results, but is hard to model; UK voters decisively rejected AV in a 2011 referendum ([20:47–20:55]).
• Voter Behavior: Under PR or AV, people might vote less tactically ([21:27]).
• Polling Miss: Pollster Ben Page (Ipsos Mori) says error wasn’t due to “shy Tories” but overestimated turnout among Labour voters ([21:33–22:00]):

  “…the main reason their polls didn't reflect the outcome was that they overestimated the Labour vote…” ([21:43])

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5. Listener Follow-Up: Shared Birthdays and Probability

[22:12–22:56]

• Listener Query: Penelope and friend both due to have babies on same day; previously discussed on show—the chance was 1 in 30 ([22:12]).
• Result: Babies were born a day apart—not exact, but close enough for joint birthday parties ([22:43–22:56])

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Notable Quotes & Moments

• “There are two proper epidemiological studies…What they show is that the overall incidence of stroke is falling.” – Prof. Tony Rudd ([02:47])
• “This one is just wrong.” – Charlotte MacDonald (on teacher dropout myths, [06:10])
• “It’s 9%.” – Sam Friedman (actual teacher dropout figure, [06:20])
• “That would take 13 years.” – Charlotte MacDonald (on how long until 40% of teachers leave, [08:01])
• “If the counter does reach that maximum… it’ll enter a fail safe mode, shut down part of the engines…” – Chris Baranjuk ([13:34])
• “When it [Gangnam Style] reached a very specific number… it actually maxed out the number of views YouTube can record at that time.” – Chris Baranjuk ([16:02])
• “A very different result then…” – Tim Harford (on PR election numbers, [19:45])
• “The main reason their polls didn’t reflect the outcome was that they overestimated the Labour vote.” – Tim Harford ([21:43])

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Conclusion

This episode of More or Less demonstrates why precise, honest use of statistics matters, whether for public health, teaching careers, computers, or elections. Misinterpretation can sow public fear or misinformation, and the show’s usual tone—measured, skeptical, and sometimes gently sly—reminds us that statistics are powerful, but must always be scrutinized.

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Useful Timestamps:

• Rising Strokes section: [00:58–05:13]
• Teacher Quitting Myth: [05:54–09:43]
• Computer Counting Errors: [10:00–16:38]
• Election/Proportional Representation: [16:38–22:00]
• Listener baby birthday probability: [22:12–22:56]

Transcript

[Tim Harford]

Thank you for downloading this programme from BBC Radio 4. I'm Tim Harford. Hello and welcome to More or Less, your weekly guide to the numbers in news and in life. This week, we abandon politics completely. Well, not completely. We will be asking, if the UK electoral system was based on proportional representation, who'd be the Prime Minister right now? But we'll also be asking whether it's true that lots of teachers quit the job before finishing their first year. And we'll be talking about computers that just journalists can't count large numbers, such as the number of times this video has been viewed. And we'll be handing out a more or less seal of approval Gold Star to a newspaper that's admitted a statistical error. But first, a number of listeners have got in touch over a news story earlier this week.

[Sam Friedman]

There's been a big increase in the number of cases of stroke among relatively younger people.

[Wesley Stevenson]

Sharp rise in the number of strokes

[Charlotte MacDonald]

among people in their 40s and early 50s.

[Wesley Stevenson]

In the past, the Strokes association says

[Tim Harford]

there's been a big increase in the

[Wesley Stevenson]

number of cases of stroke being suffered by people of working age.

[Tim Harford]

Many people seem to be skeptical about this and they've asked us to look into the numbers, which come from the Stroke Association, a charity. The Stroke association analysed hospital admissions data for NHS England and found some alarming increases. For men aged 40 to 54, for example. For example, admissions for strokes have risen over the past decade and a half by 2000 to over 6000. They've rocketed, as the Stroke association put it. Admissions for women of the same age rose by a third, and for 20 to 64 year olds in general, they rose by a quarter. As the Chief Executive of the Stroke association put it, there is an alarming increase in the numbers of people having a stroke in working age. But is there? This is Tony Rudd, a professor at King's College London and also NHS England's National Clinical Director of Stroke. He doesn't think so.

[Professor Tony Rudd]

Over the last few years, we've actually quite significantly changed our practice, so we're encouraging more people to come directly to hospital. There's been public awareness campaigns and we are admitting more patients with mini strokes to hospital than we ever used to. So the increase in the number of people coming into hospital may conceivably be due to an increased incidence of stroke, but I think it's probably more likely to be due to the fact that we're just admitting a greater proportion of patients than we used to do.

[Tim Harford]

We have a sense of what the background incidence actually is. Whether the problem is getting worse or

[Professor Tony Rudd]

better, we do have evidence that actually the problem is getting better. So there are two proper epidemiological studies going on at the moment, population based registers of stroke patients, one in Oxford and one in South London, and they've been going for a number of years now. And what they show is that the overall incidence of stroke is falling quite markedly and that is in all age groups. So the evidence from the stroke association doesn't quite fit with perhaps the more detailed scientific evidence.

[Tim Harford]

Do you think they were justified in saying that the instance of strokes has rocketed?

[Professor Tony Rudd]

No, I don't think they are justified in saying that they need to be more robust in their use of data. I would fully accept that. I don't think, whatever the reason you're doing it for, whether it's a charity or a pharmaceutical company or whatever, it's important that the data are used as carefully and as accurately as possible. I do fully understand and sympathise that the message around trying to get stroke rates down is absolutely critical. And I do understand and I sort of respect them for it. But on the other hand, it just makes me feel uneasy.

[Tim Harford]

And do you think they're justified in blaming what they say is a rise on a sedentary and unhealthy lifestyle?

[Professor Tony Rudd]

Well, I mean, we do know that sedentary lifestyle and increasing obesity and as a result increasing rates of diabetes and possibly high blood pressure as well, that that is happening as a background phenomenon and that one would accept those are major risk factors for stroke. So it's not totally off the wall to suggest that that sort of change in the pattern of, in the population might be leading to an increase in stroke incidence. The problem is that I don't think we've really got strong enough data to be able to absolutely say that's happened yet. But actually, if you look at the rates at which diabetes are increasing, if it hasn't happened already, then one would expect that it probably will do in due course.

[Tim Harford]

So to summarise, the instance of strokes, as far as we can tell, is falling, and it's falling for pretty much all demographic groups. There may be trouble ahead because of diabetes, but it hasn't happened yet. And in fact, the only thing that's increasing is hospital admissions, and hospital admissions are increasing because of better practice, higher awareness and better imaging.

[Professor Tony Rudd]

I think that's right, yes.

[Tim Harford]

Professor Tony Rudd, thank you to loyal listeners Adam Jacobs and Michael Blasland for calling our attention to this story. Michael, of course, is not only a loyal listener, but one of the founders of this program. If you have your own story or question you'd like us to investigate, please email more or lessbc.co.uk. we've all been pretty preoccupied with election related numbers recently, but if you thought that meant we or our listeners weren't keeping our bdis open for other outrageous numbers, you would be wrong. So, dear newspapers of the land, you may have thought you got this one passed us without scrutiny. You did not.

[Wesley Stevenson]

40% of teachers quit after one year

[Charlotte MacDonald]

schools lose 2 in 5 new recruits.

[Professor Tony Rudd]

4 out of 10 new teachers don't

[Tim Harford]

last a year in the classroom. We have Charlotte MacDonald in the studio and she's been looking into this. Charlotte, is this number true?

[Charlotte MacDonald]

No. Sometimes on this program we're explaining the greater context or nuances of a number.

[Tim Harford]

Numbers that are sort of true. Kind of true.

[Charlotte MacDonald]

Yeah. And this one is just wrong.

[Sam Friedman]

You get the impression from reading the newspapers that that 40% referred to people who had started their teaching career, had found it horrifying, and then decided to leave straight away. But that's just nowhere near the number of people who leave in their first year. It's 9%.

[Charlotte MacDonald]

That was Sam Friedman, who's the director of research at Teach First, a charity that trains teachers.

[Tim Harford]

And Sam Friedman says that fewer than 1 in 10 teachers are leaving after a year. So where's this story come from?

[Charlotte MacDonald]

The papers got the story from a speech at the annual conference of the association of Teachers and lecturers union, or ATL. The general secretary, Dr. Mary Bousted In 2011, the latest year for which figures are available, just 62% of newly qualified teachers who gained QTS that year were still in teaching a year later.

[Tim Harford]

So she said the statistic the other way round. Only six out of 10 new teachers are teaching after a year.

[Charlotte MacDonald]

Yeah, cleverly phrased because the other four in ten aren't necessarily getting teaching jobs and then quitting in disgust. The ATL has included newly qualified teachers who haven't got teaching jobs in the first place. For all we know, they took a year out, got a job in another industry, or went into an educational job that isn't captured in these figures. For example, teaching in the independent sector or overseas.

[Tim Harford]

Where Does Sam Friedman's 1 out of 10 figure come from then?

[Charlotte MacDonald]

He's got that from a table from the National College for Teaching and Leadership, which shows what happens to newly qualified teachers in state schools in England.

[Tim Harford]

Sam Friedman told us that 9% quit within a year. So how long before we get to the numbers that the newspapers were reporting? Where 38% or 40% of teachers have quit.

[Charlotte MacDonald]

OK. That would take 13 years. The majority of teachers stay in the job for well over a decade.

[Tim Harford]

So the ATL union phrased the statistic in a confusing way and the newspaper interpretation of that statistic was just wrong.

[Charlotte MacDonald]

Yeah. Now, one of them, the Independent, has come out and apologised for misreporting this figure. So well done to the Indy. Get a more or less gold star.

[Tim Harford]

Yeah, we should give them a badge. What did the ATL union say?

[Charlotte MacDonald]

The union gave us a statement from Dr. Mary Bousted, General Secretary. She said it is difficult to find reliable data on the precise scale of the teacher retention problem. Our figure was arrived at in good faith using government statistics. No one can be sure of the exact numbers leaving. Although if a recent study by the Cabinet Office is to be believed, teacher morale isn't that bad. That study isn't terribly transparent, so I wouldn't set too much store by it. But it did suggest that out of 274 different careers, primary school teachers were in the top 5% most satisfied with their jobs. Secondary school teachers also rated their jobs highly.

[Tim Harford]

Basically, teachers like their jobs, but according

[Charlotte MacDonald]

to Sam Friedman, retention isn't the big problem, it's recruitment.

[Sam Friedman]

If there are figures out there that 40% of people leave in the first year, that is completely wrong. That might put someone who's thinking about teaching off going into training in the first place, which would be pretty bad, given that we have a recruitment problem at the moment. And actually, a couple of people contacted me after I wrote about this to say they'd forwarded it on to friends of theirs who were doing teacher qualifications and thought maybe they were going to pull out because it looked so horrific. So numbers do really change the way people think about their careers and if they're misled by this, we could lose a lot of good teachers.

[Tim Harford]

Sam Friedman, Charlotte MacDonald. Thank you, Charlotte.

[Professor Tony Rudd]

Set CES Sign Cat Trois de Unite Feu

[Tim Harford]

Allimag In June 1996, the first Ariane 5 rocket took off from the European Space Agency's launch site in French Guiana. The launch marked almost a decade of hard work and billions of dollars of investment. The scientists involved were working on a mission to study how the solar wind affects the Earth's magnetic field. It was called the Cluster project. I'm sure there's a joke in there somewhere, because the rocket veered off course and only 37 seconds into its flight exploded. The failure wasn't caused by human error, error or a mechanical problem, but simply because the Rocket's onboard computer got its maths wrong. It's an example of what's called integer overflow, when a number's too big for a computer to handle. And it affects all sorts of things, from planes to pop music, as the freelance science and technology journalist Chris Baranjuk has been telling me. So, Chris, what went wrong with Ariane 5's computers?

[Chris Baranjuk]

Ariane 5 was a very advanced spaceship that's still actually used today as a rocket. In 1996, it was its first flight and they had developed the software based on the previous generation of rockets, the Ariane 4. And there were some assumptions about how Ariane 4 would work that were essentially ported over to the new rocket. In fact, this rocket actually behaved quite differently. There was a number in the software that was trying to be converted from a large space in the computer's memory into a much smaller one. And consequently that number didn't fit. So it switched into this shutdown mode and a self destruct sequence was initiated.

[Tim Harford]

So it blew itself up like in the Bond movies.

[Chris Baranjuk]

Pretty much 37 seconds into its flight, it ended in a ball of fire. Expensive, very expensive. Hundreds of millions of pounds. And of course, the European Space Agency had spent billions developing it in the first place. So it was a very, very bad start.

[Tim Harford]

So just to understand this idea of putting a large number in a small space, this is like trying to count above a hundred and you've only got two digits. You've got a cricket scoreboard and no one's ever expected to score a century, or maybe no one's ever expected to score a thousand runs. So you've got three slots on your cricket scoreboard. You can register 100 or 200 or 300 or even 350 odd if you're Kevin Peterson. But no one's ever expected to score 1000. And so you don't have that fourth digit on the cricket scoreboard. And it's sort of like that, only in computer language.

[Chris Baranjuk]

That's a good way of thinking about it. And the key part of your explanation there is that there is an assumption at the heart of that no one's ever expected to score that many points. The board isn't built to carry that big a number. So this is what computers do. In many cases, this counter will simply roll over and go back to zero. And actually there are lots and lots of examples of this. Only 2 weeks ago it was announced by the Federal Aviation Administration in the states that Boeing 787 aircraft suffer from exactly the same sort of problem. There's a counter in software on the control unit which drives power to the plane's engines. And that counter will max out if the plane has been left on for more than 248 days. So the advice from the FAA was simply to switch the plane off and on again, because then you'll restart the

[Tim Harford]

counter, but ideally not in mid air,

[Chris Baranjuk]

ideally not in mid air. But this is a big problem because if the counter does reach that maximum, even if the plane is in midair, it'll enter a fail safe mode, shut down part of the engines, and so, you know, the potential for catastrophe is certainly there.

[Tim Harford]

But hang on, if I can't trust a computer to count to a big number, what can I trust a computer to do? I mean, how is it possible that computers actually cannot cope with large numbers? You would have thought it was the most straightforward thing in the world for a computer.

[Chris Baranjuk]

It sounds really weird when you think about, first of all the fact that computers seem so capable of doing certain tasks, and secondly that numbers are infinite. The two concepts seem to jar quite, quite nasty really. But the problem is if you're building a computer system, you want to make sure that it's going to run as efficiently as possible. So you're going to choose storage spaces for the numbers that you store, which have limitations based on the assumptions that you'll make about what that computer will actually do. There's no point building a computer that can store an infinitely large number if you only need to do something like in our example, count the score of a player in a game.

[Tim Harford]

So the classic example of this is clearly the millennium bug, which hopefully some loyal listeners would be too young to remember. But I remember very clearly the panic as we reached the end of the 20th century and suddenly realized all these computers were set, or some computers were set just to count the years in terms of the last two digits. I used the word panic because people were very concerned about this and nothing really seemed to happen or did it.

[Chris Baranjuk]

A lot of computer programmers would be very upset if you said nothing seemed to happen because of two things. One, they worked very, very hard in the years preceding the year 2000 to actually patch software and introduce fixes for these things. You can go back to the mid-90s and people are already talking about what they're going to have to do in the advent of the year 2000. And the second thing is that, well, yes, these bugs did actually cause some errors in the early days of the current millennium. So you can go online, you can find plentiful examples of this There were signs at train stations that said the year was 1900. There were websites which gave the year as a series of five digits, 19100100 years after 1900, which is certainly correct, but it's not the way we would write that year. Another famous example that came up quite recently in December actually was Gangnam Style. Very popular song on YouTube had actually maxed out YouTube's view counter when it reached a very specific number of views, which was 2,147,483,647. It actually maxed out the number of views that YouTube can record at that time. But YouTube then of course updated its software to carry a larger number and the new maximum is now well over 9 quintillion. So it'll be quite a while before Gangnam Style reaches that limit.

[Tim Harford]

Chris Baranjuk and Chris first wrote about the trouble that computers can have with big numbers in an article for the BBC Future website. You're listening to More or Less with me, Tim Harford. Our email address is more or lessbc.co.uk in the wake of the general election, there were protests on the streets of London by people angry at the result. Of course it hurts to lose an election, especially if you weren't expecting to lose. But partisanship aside, the protesters do have a point. The Conservative Party won an overall majority of the seats with only 37% of the vote. According to the London School of Economics, this election was one of the least proportional in post war history. Well, Wesley Stevenson is here to tell us more.

[Wesley Stevenson]

Yes, loyal listeners have been writing in to ask what difference proportional representation would have made to the election result. For years when there were only really two parties in British politics, the first past the post system delivered results that were pretty close to proportional representation. Let's return to the election night of 1955. I think the first thing to do is to look at the result so far in terms of seats. Here you see the conservatives 339 seats. Well I think that when the final results are in the four more seats, they're likely to go to the Conservatives. In the end The Conservatives got 344 seats. That's 55% from just under half the vote. And Labour got 44% of the seats from 46% of the vote. So in terms of proportionality, well, it was a lot closer than this year's election.

[Tim Harford]

Anyway, we know that last week the conservatives got 37% of the vote but a majority of the seats. So how, how far away from proportional Representation was that election result.

[Wesley Stevenson]

If you look at the average number of votes per seat for each party, the Conservatives, they averaged around 34,000 votes for every seat they got. Labour 40,000. The SNP, they got their seats really cheaply with an average of 26,000 votes per seat. Now look at the Greens who polled more than a million votes for their one seat, and UKIP who polled almost 4 million votes for their one seat.

[Tim Harford]

So what if we re ran the election using a system of proportional representation?

[Wesley Stevenson]

There are a few estimates out there based on various different voting systems, but let's look at the straight PR system. The proportion of votes equals the proportion of seats. We invited the returning officer for Trumpetonshire to read out the results. Under this new system, I, Sir Gordon Murray, being the returning officer for the election of all members of Parliament in England, Scotland and Wales, do hereby give notice that the number of seats recorded for each party is as 242. Labour 199. Liberal Democrats 51, Ukip 82, SNP 31, Plaid Cymru 3, the Green Party 24.

[Tim Harford]

A very different result then. The Liberal Democrats 51 seats instead of 8. Ukip 82 seats instead of 1. The SNP, almost half as many seats as they got in the actual election. The Green party up from 1 in last week's election to 24 under proportional representation. Although one thing wouldn't have changed, which is that the Conservatives would still have been the largest party.

[Wesley Stevenson]

Yes, and David Cameron might still have been Prime Minister if he was able to reach some arrangement with Ukip, because together Ukip and the Conservatives would have 324 seats, which would give them a very slim majority.

[Tim Harford]

What about other voting systems, Wes?

[Wesley Stevenson]

The other systems are trickier to model. One alternative is the small district system, which gives you proportional representation over each district of four or five MPs. It's similar to the method used in the European elections. Another possibility is the alternative vote system, where voters in each constituency can vote for a minor party and then their votes are transferred to a party that is more likely to win.

[Tim Harford]

The alternative vote system was, we should say, offered to the electorate in 2011 and decisively rejected in a referendum.

[Wesley Stevenson]

It was indeed. And it's hard to say for sure what might have happened under these systems, especially in av, because we can only guess at people's second preferences. But generally the result is somewhere between the current first past the post system and pure proportional representation. UKIP always does better, the Conservative, Conservatives and Labour always do worse and we would have a hung parliament with the Conservatives as the largest party. But this assumes that people would vote in the same way under these systems. There is evidence to suggest they would vote less tactically.

[Tim Harford]

And before we leave the election, Wes, a word on the polls and why they got it so wrong.

[Wesley Stevenson]

Yes, pollster Ben Page from Ipsos Mori, who was on last week, he's released his initial assessment of the reason the polls were wrong and he says it wasn't the famous shy Tory effect, but instead lazy Labour Labour Party voters who said they would show up and vote but didn't. As Ben told us last week, the main reason their polls didn't reflect the outcome was that they overestimated the Labour vote. The other parties, they say they got pretty much correct.

[Tim Harford]

Well, that's his excuse anyway. Thank you, Wes. You are listening to More or less. Back in February we were feeling broody when loyal listener Penelope Cheney got in touch to say I'm expecting a baby

[Wesley Stevenson]

in April and discovered that one of

[Tim Harford]

my close friends is also expecting a baby on the same day. We calculated that there was a 1 in 30 chance of both Penelope and her friend Eleanor having their babies on the same day. Not too bad. But there was a much, much smaller chance of that day actually being the due date, April 4th. We were wondering what had happened when this message came through on the more or less answerphone. Hi, this is Eleanor.

[Professor Tony Rudd]

Just to let you know, our daughter

[Tim Harford]

Juliet Imogen was born on Saturday 11

[Professor Tony Rudd]

April, which is about 24 hours after Penelope had her little boy. So sorry we didn't quite manage to coordinate for you.

[Tim Harford]

So Penelope's baby boy arrived six days after his due date and Eleanor's baby arrived one day later. I think that is still close enough for them to have joint birthday parties. Thank you for letting us know Eleanor and we wish both famil is all the best. That's all we have time for this week, but as always, please drop an email To More or lessbc.co.uk if you have any questions. You can also subscribe to our free download and listen to us on Shuffle if you like. That'[e-mail] more or less or you can just listen to the radio same time, same place next week. Goodbye. And just a reminder that you can download more [e-mail] Radio 4.