Annual Survey of Hours and Earnings (ASHE)
The Annual Survey of Hours and Earnings (ASHE) is based on a 1% sample of employee jobs taken from HM Revenue and Customs PAYE records. Information on earnings and hours is obtained from employers and treated confidentially. ASHE does not cover the self-employed nor does it cover employees not paid during the reference period. In 2013 information related to the pay period which included 17 April.
Summary Quality Report
A Summary Quality Report (pdf) for ASHE describes, in detail, the intended uses of the statistics, their general quality and the methods used to produce them.
Common pitfalls in interpreting the series
The headline statistics for ASHE are based on the median rather than the mean. The median is the value below which 50% of employees fall. It is ONS's preferred measure of average earnings as it is less affected by a relatively small number of very high earners and the skewed distribution of earnings. It therefore gives a better indication of typical pay than the mean.
Various methods can be used to measure the earnings of women relative to men. ONS's headline estimates of the gender pay gap are for hourly earnings excluding overtime. Including overtime can distort the picture as men work relatively more overtime than women. Although median and mean hourly pay excluding overtime provide useful comparisons of men's and women's earnings, they do not reveal differences in rates of pay for comparable jobs. This is because such measures do not allow for the different employment characteristics of men and women, such as the proportion in different occupations and their length of time in jobs.
In March 2012 the 2011 ASHE estimates were published on a Standard Occupational Classification (SOC) 2010 basis (they had previously been published on a SOC 2000 basis). Since the SOC forms part of the methodology by which ASHE data are weighted to produce estimates for the UK, this release marked the start of a new time series and therefore care should be taken when making comparisons with earlier years.
Similarly, methodological changes in 2004 and 2006 also resulted in discontinuities in the ASHE time series.
The earnings information presented relates to gross pay before tax, National Insurance or other deductions, and excludes payments in kind. With the exception of annual earnings, the results are restricted to earnings relating to the survey pay period and so exclude payments of arrears from another period made during the survey period; any payments due as a result of a pay settlement but not yet paid at the time of the survey will also be excluded.
For particular groups of employees, changes in median earnings between successive surveys may be affected by changes in the timing of pay settlements, in some cases reflecting more than one settlement and, in others, no settlement at all.
Most of the published ASHE analyses (that is, excluding annual earnings) relate to full-time employees on adult rates whose earnings for the survey pay period were not affected by absence. They do not include the earnings of those who did not work a full week, and whose earnings were reduced for other reasons, such as sickness. Also, they do not include the earnings of employees not on adult rates of pay, most of whom will be young people. More information on the earnings of young people and part-time employees is available in the main survey results. Full-time employees are defined as those who work more than 30 paid hours per week or those in teaching professions working 25 paid hours or more per week.
Revisions: In line with normal practice this release contains revised estimates from the 2012 survey results which were published on 22 November 2012. These results take account of some corrections to the original 2012 data that were identified during the validation of the results for 2013, as well as late returns.
Sampling Error: Sampling error results from differences between a target population and a sample of that population. Sampling error varies partly according to the sample size for any particular breakdown or domain. Indications of the quality of ASHE estimates are provided in the form of coefficients of variation (CV). The coefficient of variation is the ratio of the standard error of an estimate to the estimate, expressed as a percentage. Generally, if all other factors are constant, the smaller the CV the higher the quality of the estimate. Nomis displays the associated CV next to each earnings estimate.
Non-sampling error: ASHE statistics are also subject to non-sampling errors. For example, there are known differences between the coverage of the ASHE sample and the target population (i.e. all employee jobs). Jobs that are not registered on PAYE schemes are not surveyed. These jobs are known to be different to the PAYE population in the sense that they typically have low levels of pay. Consequently, ASHE estimates of average pay are likely to be biased upwards with respect to the actual average pay of the employee population. Non-response bias may also affect ASHE estimates. This may happen if the jobs for which respondents do not provide information are different to the jobs for which respondents do provide information. For ASHE, this is likely to be a downward bias on earnings estimates since non-response is known to affect high-paying occupations more than low-paying occupations.
Further information about the quality of ASHE, including a more detailed discussion of coverage and non-response errors, is available on the ONS website.
Response: The 2013 ASHE is based on approximately 184,000 returns.