Consider these three claims. In 2004, it was predicted that the number of problem gamblers would double to 750,000 if the Gambling Bill became law.

In 2013, it was reported that the number of problem gamblers had doubled in the previous six years and had reached 450,000.

Last month, it was reported that the number of problem gamblers had doubled in the last three years and had reached 336,000.

How does the number of problem gamblers keep doubling without it increasing? Let’s take a look…

Back in 2004, when that nice Mr Blair was trying to liberalise the gambling market, a prediction was made…

Public Health Association chairman Geoff Rayner said the number of addicts could double if the plans went ahead… He highlighted research by the Henley Centre, a strategic marketing consultancy, which estimated the number of gamblers could double to 750,000 people.

You don’t need to be Carol Vorderman to work out that there were approximately 375,000 problem gamblers in 2004.

Mr Blair got his liberalisation (or most of it) and we have had gambling advertising on TV and a somewhat more relaxed approach to casinos ever since. We have also seen the rise of fixed-odds betting terminals and online gambling, both of which were supposed to drag us to perdition.

What happened next? The popular narrative is that there was an epidemic of problem gambling. Take this, from the *Independent* in January 2013, for example…

A huge increase in gambling addicts will make Britain’s obsession with online betting a £2bn business. New evidence reveals that the number of people in danger of becoming problem gamblers has reached nearly a million, while hardcore addicts have doubled in six years to almost 500,000.

What the *Independent* calls ‘hardcore addicts’, the British Gambling Prevalence Survey calls ‘problem gamblers’ and it is the number of problem gamblers that was estimated in the 2010 survey. The *Independent* was citing that survey, although it exaggerated the number. As it noted later in the article, the survey’s mid-point estimate was 450,000.

So not actually a doubling, but still a rise, right? Not necessarily. The only firm conclusion drawn in the 2010 British Gambling Prevalence Survey was that there were between 254,900 and 593,400 problem gamblers in the UK. The wide gap between the low and high ends of the estimate meant it was uncertain whether there had been any rise at all since the previous survey of 2007.

Nevertheless, a narrative had been set in motion that problem gambling had doubled and it was all the fault of online gambling/fixed odds betting terminals/advertising.

Last month, the *Times* reported (not for the first time) that the number of problem gamblers had doubled again.

The number of people with a severe gambling problem has almost doubled to 336,000 in the past three years, according to the Gambling Commission.

But hang on a moment. 336,000 is less than it was in 2004 when Geoff Rayner made his gloomy prediction — and the rate of problem gambling has supposedly doubled twice since then.

Fortunately, there is a simple explanation. There are not enough problem gamblers for surveys to estimate the number with any precision. Since 1999, when the first survey was conducted, the rate has ranged from 0.3 per cent to 0.9 per cent of the adult population. The high of 0.9 per cent was recorded in 2010 and the low of 0.3 per cent was recorded in 2013. There is no pattern, no trend, but there is random fluctuation.

So this is what happens: when the rate appears to go up, the media report it. When it appears to go down, they don’t. The *Independent* compared the 2010 estimate to the 2007 estimate. The *Times* compared the 2016 estimate to the 2013 estimate. Nobody compared the 2013 estimate to the 2010 estimate, but if they had they could have claimed that the rate of problem gambling had more than halved.

None of it means anything. In practice, the estimates have such wide confidence intervals (or margins of error, if you like) that one year’s data is statistically indistinguishable from another. Give or take a few fractions of a percentage point, the rate of problem gambling in Britain is 0.5 per cent and has been ever since we started trying to measure it.