National Minimum Wage

Appendix 4: Main Data Sources
that differ from the headline aggregates published by ONS, but the estimates of proportions
are affected less.
10 ASHE contains no information on disability, ethnic background, country of birth, nationality or
education level. The LFS is, therefore, our only source of data on earnings for disabled
people, ethnic minorities, migrants and people with no qualifications. However, data on pay
and hours in the LFS tend to be less reliable than in ASHE. Reasons for this include: a smaller
sample; people often answering the earnings questions without reference to pay
documentation (although they are prompted to consult available documents); and some
information being provided by proxy respondents. ASHE collects information from employers
about employees’ paid hours, whereas the LFS collects information from individuals about
their actual and usual hours of work, which might include unpaid hours. This generally means
that derived hourly earnings from LFS are below the derived hourly pay rates recorded in
ASHE. Where a stated hourly rate of pay is unavailable from the LFS, ONS has developed an
imputation method using a nearest neighbour regression model, which also takes account of
information on second jobs. This methodology reduces the differences between hourly
earnings estimates from the LFS and ASHE, and we use it to estimate earnings in our LFS
analyses.
11 The LFS started using SOC 2010 in the first quarter of 2011. This and subsequent datasets
retain some high-level SOC 2000 variables, but they are not detailed enough to identify the
low-paying occupations. As we have not yet been able to define the low-paying occupations
using SOC 2010 we have not used the LFS for any analyses of low-paying occupations in this
report, but we intend to do so in future reports.
12 In this report the data we have presented on disabled people have used the old definition of
working age (men aged 16-64 and women aged 16-59), rather than all aged 16-64, in order to
allow the data to be consistently compared across time. The LFS changed the way it asked
questions on disability in 2010, which caused a discontinuity in the time series. Prior to 2010
most women aged 60 or over were not asked whether they had a work-limiting disability.
Since the state pension age for women started to increase (in April 2010) the question has
been asked of all women aged 60-64. Men were not affected by this change. Until there are
sufficient data on the new basis to form a substantive time series, we will continue to use
the old working age definition for analyses of disabled people.
Employee Jobs
13 The employee jobs series provides a timely industrial breakdown of jobs in the UK. A number
of Short Term Employer Surveys, which collect data from businesses across the economy,
are used to compile the employee jobs series. Data at a more detailed level, however, are
available only for Great Britain and are not seasonally adjusted. This makes quarter-to-quarter
comparisons problematic, particularly as much of the employment in the low-paying sectors
is of a seasonal nature, for example Christmas trading in the retail sector. Comparisons
between one quarter and the same quarter a year earlier, however, help to alleviate this
particular problem. Other than the annual benchmarking exercise, there were no substantive
revisions to the data.
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