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Calculation of full-day equivalent working days lost estimates and rates

Estimating working days lost due to work-related illness and workplace injury

Individuals employed in the last 12 months reporting a work-related illness were asked how much time they took off work because of their illness (the most serious if more than one was reported) in the 12 month period prior to interview. It includes time lost due to all episodes of the illness in the 12 month period.  Responses were assigned, by the interviewer, to one of ten categories of days, weeks or months (See Annex 2). A value has been ascribed to each of these groups that represents an estimated average number of days off for the category in question. This was achieved by exploring the distribution of absence durations graphically, and by examining other related information e.g. Department for Work and Pensions' Incapacity Benefit data and results from earlier surveys. The estimated average working days lost used for each days lost category are shown in the table below.

Summary of average working days lost by days off category

Days lost category Estimated average working days lost
No time off work 0
Less than 1 day   0.5
1 to 3 days 2
4 to 6 days 5
At least 1 week but less than 2 weeks 7
At least 2 weeks but less than 1 month 15
At least 1 month but less than 3 months 41
At least 3 months but less than 6 months 93
At least 6 months but less than 9 months 160
At least 9 months but less than 1 year 245

Individualsemployed in the last 12 months reporting a workplace injury, were asked how soon they were able to return to work after the accident.  This information was reported in actual elapsed days (or weeks/months where the respondent couldn't recall the number of days and converted with the use of a standard coding frame to number of days) between injury and returning to work and does not include any subsequent time taken off work.

Converting reported working days lost into full-day equivalent working days lost

Estimates ofworking days lost are expressed in the form of full-day equivalent (FDE) working days to take account of variation in the daily hours worked (for example part-timers who may work a shorter day or people who work particularly long hours).   Full-day equivalent working days are calculated by adjusting the days lost estimates using the ratio of the individual's usual weekly hours to the average usual weekly hours of all full-time workers estimated using the LFS.  For this purpose, hours of work excluded overtime and meal breaks in line with the New Earnings Survey definition of full-time/part-time.  Furthermore, the LFS only collects information on hours of work for current workers.  Therefore, appropriate usual hours, based on employment characteristics, were imputed for people who worked in the last 12 months but who were not working at the time of interview.  Usual hours were also imputed for those current workers who did not answer the relevant usual hours of work question.

Average hours worked per week by full-time workers is based on 2001/02 data and remains constant in later surveys, allowing trends over time to be measured which takes account of changes in usual hours worked.

Estimated annual FDE
working days lost
= Σ [ usual hours worked per week
Average hours usually worked per week by full-time worker
x  working days lost]

Converting the number of workers into the number of full-time equivalent workers

Rates of working days lost are expressed in terms of average annual working days lost (full-day equivalent) per full-time equivalent worker to take into account the difference in time worked by full and part-time workers.  Full-time equivalent workers are calculated as the sum of the ratio of individuals usual weekly hours to the average usual weekly hours of all full-time workers estimated using the LFS for current workers i.e. those working in the LFS reference week.  Again the average full-time usual hours has been based on 2001/02 data (at 40.6 hours) and remains constant in later surveys.

FTE = Σ (usual hours worked per week)
average hours usually worked per week by full-time worker
Updated 2013-10-25