There is a broadly consistent time series for:
Whilst the small change in survey period from December-February for years prior to 2006/07 to January-March from 2006/07 onwards may have potentially introduced a discontinuity to these data series, preliminary investigations suggest that this change in survey design has not affected the top level injury, ill health and working days lost data. Further work is planned to explore the possible effect of this small change in survey period. Because of the potential discontinuity, comparison of 2006/07 data with earlier years at more disaggregated levels should be made cautiously.
The above surveys had the same design and coverage (with the exception of the small change in survey time period in 2006/07) and used the same methods to adjust for non-response to the screening questions in each survey. Also the survey data has been weighted to post-2001 census population estimates (the 2001 Census showed that the UK population was around 1 million lower than previously estimated and in March 2004 revised LFS weighting factors were released).
For earlier surveys, because of the difference in design, coverage, level of information collected, methods used to adjust for non-response to the screening question in each survey and the use of pre-2001 census population weights it is only possible to make broad based comparisons, and even these need to be treated with caution. To achieve even these broad based comparison for illness data, a number of adjustments have to be made to the data to ensure comparability.
