Table 1

Data sources for economic evaluation

Impact	Data required	Data source
Intervention costs
Footwear purchase costs. At the societal level, the purchase of the intervention footwear will displace the purchase or wear of other footwear, so additional costs are likely to be minimal.	Pairs of footwear distributed, unit cost of footwear, effective lifetime of footwear.	Purchase costs already known. Data on effective lifetime of footwear to be collected during follow-up of 45 trial participants.
Managerial and staff time incurred in distributing footwear and communicating the intervention.	Given that the National Health Service (NHS) already has dress requirements and provides staff uniform, we expect that any additional staff time incurred in rolling out the slip resistant footwear will be negligible, so we do not propose to quantify this impact.
Avoided costs (benefits)
Loss of productivity/output due to worker absence. Loss of ‘production’ (in terms of services provided) to the NHS is likely to be minimised where hospitals recruit agency/bank staff to temporarily replace absent workers. The main costs to the NHS from worker absence would therefore be the costs of replacement agency/bank staff. At the societal level, a worker unable to work due to injury represents a reduction in the productive capacity of the economy.	Number of full-time equivalent working days lost due to slip-related injuries by type of worker. Average daily costs of agency/bank workers by role (including agency fees)	Trial data on reduction in slip injuries and full-time equivalent days lost, supplemented by the Labour Force Survey data on working days lost due to slips, trips and falls in the healthcare sector. Maximum rates for agency wages published by NHS improvement. Pay rates for bank staff published by NHS Trusts.
Staff sickness payments made to workers absent due to slip-related injury. This is not a cost at the societal level, since the payments are a transfer from employer (NHS) to employees.	Expected reduction in injuries resulting from slips in the NHS (using data from trial or modelled as discussed later in this protocol), the reduction in time off work associated with these avoided injuries, and NHS occupational sick pay policy (the trial excludes temporary/agency staff). Average daily staff costs (wages plus non-wage costs, such as national insurance and pensions contributions).	Trial data on full time-equivalent days lost as above. NHS occupational sick pay policy is set out in the NHS Terms of Conditions and Service Handbook. This will be used to model sickness payments based on time off work and staff wage rates. NHS staff wage rates by job band publicly available. Supplemented by data from the Annual Survey of Hours and Earnings where necessary and the ONS/Eurostat Labour Costs Survey (for non-wage costs).
Healthcare treatment costs incurred due to slip-related injuries.	Healthcare resource use, unit healthcare treatment costs.	Data on healthcare resource use to be collected in the study trial (14-week questionnaire). This will be costed using NHS Reference Costs unit costs database. Supplemented where necessary by published data on healthcare treatment costs for relevant injury types from published sources where available, and Health and Safety Executive (HSE) ‘Costs to Britain’ estimates of healthcare treatment costs for injuries.
Compensation (including legal) costs, arising from staff claims following injury under the NHS Liabilities to Third Parties Scheme (LTPS). At the societal level, the analysis will account for the transfer payment from staff claimants via the scheme.	Average compensation costs to NHS per case due to slip related injuries. This will be based on historical data as any claims from injuries sustained during the trial period are unlikely to be determined before the completion of the study.	NHS Resolution data on non-clinical compensation claims and payments under the NHS LTPS arising from slip-related staff injuries.
Administrative costs—reporting of slip injuries (RIDDOR), processing sickness payments, dealing with insurance and compensation claims.	Amount of staff time spent processing payments, claims, etc, plus wage rates of staff.	This is likely to be a small, if not negligible, impact. Could be valued using generic estimates from HSE Costs to Britain model of the typical costs per injury case.