Unemployment, one would reasonably assume, is the state of not being employed. Following this logic, by adding together all the employed people and unemployed people of working age in Britain you would expect to get all the people of working age in Britain. According to official statistics, the employment rate is 74.2 per cent. But the unemployment rate is just 6 per cent – 1,864,000 people.

That leaves one person in five unaccounted for: neither employed, nor unemployed. It gets more confusing.

According to another set of official statistics, the unemployment rate is just above one million. Grouping people (who are messy) into categories (which are distinct) has always been the statistician’s downfall. Is an ex-Lehman’s banker, currently drinking last year’s bonus in a Goan beach bar, unemployed? What about an ex-miner, who would like to do light work but lives in an industrial area and claims incapacity benefits?

There are 1,071,900 people currently claiming jobseeker’s allowance. Everyone agrees that they are unemployed. But most statisticians also agree that there are plenty of unemployed people who are not on the dole. If your partner works, if you have savings above a certain level, or if you are outside a set age range, then you may not qualify for jobseeker’s allowance. And some people just decide, for whatever reason, not to claim.

The best estimate of unemployment is calculated by the Office for National Statistics. It uses a definition set by a United Nations agency, the International Labour Organisation. This rate counts people who want to work, are available to work, and are actively seeking employment – based on survey data. This brings the rate for August to October – the earliest period for which data is available – to 6 per cent, the highest since 1999.

What, though, of the missing one in five? For the same period, there were 7.9 million people over 16 and below retirement age who were classed as “economically inactive”; 2 million of those were students; 2.3 million said they were looking after a family or home; and another 2 million were long-term sick. None of them is counted as unemployed, whatever definition is used.

But, when questioned, 2.1 million of them said they would like a job. If they were included, the unemployment rate would rise to just under 4 million.

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