Thank you for downloading the more or less podcasts from the BBC, statistically proven to be the very best numbers programme around.

This is the extended edition of the programme, first broadcast on BBC Radio 4.

Hello and welcome to a brand new series of more or less your weekly guides to the numbers in the news and in life.

With every last number of 2014 safely totted up and the unfilled database of 2015 stretching out ahead of us, it's time to find our bearings by asking our favourite people to tell us their favourite numbers of the year just passed or occasionally the year to come.

We're better to start than with David Schpiegelhalter, a man who received a knighthood last year for his services to this programme. I'm sorry, his services to statistics.

My number is 5.7 billion pounds. This was the amount that the Office of National Statistics estimated that prostitution contributed to the economy in 2012 and the reason they had to do this is that EU has now regulated that both prostitution and illegal drugs should be part of national accounts and contribute to GDP.

Now, where do they get this figure from? It's quite difficult to judge. Is that big? Is that small? It's a big number. But the ONS nicely give us a simple spreadsheet and say roughly where they got it from, they estimated around 61,000 people working in prostitution in the UK, average cost per visit, about 67 pounds, and that each was seeing about 25 clients a week and working 52 weeks a year.

Multiply those up and you get 5.7 billion pounds. Now, this figure has been questioned by people close to the profession as being far too high and I actually agree with them.

If we go through those components, the 61,000 probably isn't too bad. It's very difficult to estimate and the trade is changing so rapidly in that the number of independence now with the internet has grown enormously. You can go onto one website and see 30,000 people operating independently.

But they also take your word for that on that day. Yes, exactly. I don't necessarily recommend it, but doing this research, the numbers are there.

The numbers are there and they also get services and costs and the average cost of 67 pounds probably isn't too bad. It might be a bit low. But again, it says a profession is a hugely variability between street walking to high class escorts.

Probably those numbers aren't too bad. The crucial thing is this assumption that each person working is seeing 1200 clients a year and this seems very high indeed.

And we can do a few little so reality checks on this. It would mean, for example, that everybody working prostitution was actually turning over 100,000 pounds a year and this doesn't seem plausible from people who know about these things.

We can also say that the ONS assumptions mean that there's 75 million visits to prostitutes every year in this country as one and a half million a week.

Now, from an alternative source than latest Natsal survey on sexual behavior, estimate that around about 4% of men between 18 and 65 report paying for sex in the last five years and over the last year probably figures about about half a million.

And maybe an underestimate, but probably not too bad. Half a million men paying for sex every year in this country. And you may think that sounds quite a lot, but in order to get to one and a half million visits per week, each would have to be buying sex three times a week.

And that does not reflect as far as one can see behavior. So I guess my feeling is that this figure is too high. I know ONS are looking into it again. It'll require, you know, I think really quite a subtle approach in order to get a more realistic figure and I predict it's going to come down substantially.

I mean, you do slightly feel for the office for national statistics, because unlike you, David, they're not experts in this X trade, but it's quite quite difficult to find out all of these things.

But I suppose what you're saying is that the back of the envelope should have been enough to call into question this headline.

Exactly. It's one of those things where, you know, actually a real back of the envelope calculation can be enormously advantageous.

They know ONS have been using, you know, some of these sites, they're, they, for example, to get their prices used.

One of the review sites that exists for reviewing prostitution much in the same way as it's trip advisor does for hotels.

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