11. Strengths and limitations

Accuracy of the statistics: estimating and reporting uncertainty

The figures in this bulletin come from surveys, which gather information from a sample rather than from the whole population. The sample is designed to be as accurate as possible given practical limitations such as time and cost constraints. Results from sample surveys are always estimates, not precise figures. This can have an impact on how changes in the estimates should be interpreted, especially for short-term comparisons.

As the number of people available in the sample gets smaller, the variability of the estimates that we can make from that sample size gets larger. Estimates for small groups (for example, unemployed people aged between 16 and 17 years), which are based on quite small subsets of the Labour Force Survey (LFS) sample, are less reliable and tend to be more volatile than for larger aggregated groups (for example, the total number of unemployed people).

In general, changes in the numbers (and especially the rates) reported in this bulletin between three-month periods are small, and are not usually greater than the level that can be explained by sampling variability. Short term movements in reported rates should be considered alongside longer-term patterns in the series and corresponding movements in other sources to give a fuller picture.

Further information is available in A guide to labour market statistics.

Where to find data about uncertainty and reliability

Dataset A11 shows sampling variabilities for estimates derived from the LFS.

Sampling variability information for average weekly earnings growth rates is available from the “Sampling Variability” worksheets within datasets EARN01 and EARN03.

The sampling variability of the three-month average vacancies level is around plus or minus 1.5% of that level. Information on revisions is available in the labour market statistics revisions policy.