The government calculates the total number of people unemployed by using the claimant count. This consists of all the people who sign on at their local job centre.

This figure will never be totally accurate because:

Some people who are out of work do not sign at their job centre
Some people who do sign on actually have jobs on the side
People are sometimes between jobs and there may be a time lag with statistics
Of the large numbers of people and job centres involved
Seasonal Adjustment

The claimant count figure is adjusted to take account of seasonal fluctuations. When Building workers are paid off in the winter due to bad weather they are not really losing their jobs, even though they are signing on, so they would not be included in the total unemployed figure. This means that unemployment figures show accurate underlying trends not temporary fluctuations.

Fruit pickers being hired

Unemployment figures can also be seasonally adjusted upwards. At Christmas time many people find jobs on a temporary basis. Although they would not be signing on they would be included in unemployment figures to show the real underlying trend i.e. unemployment is not really falling.

building site closed

The Labour Force Survey

Recently, the UK Government has used a large survey of the labour force to estimate unemployment figures. They find out what has happened to the sample and use these figures to estimate what has happened to the total unemployed.