Unionisation and injury risk in construction: a replication study

Objective: To replicate, in a more recent time period, a previous cross-sectional study to estimate the association between unionisation and the risk of workers' compensation injury claims. Methods: The sampling frame was workers' compensation company account records in the industrial, commercial and institutional construction sector in the province of Ontario, Canada, 2012-2018. Company unionisation status was determined through linkage with records of unionised contractors. Outcomes were cumulative counts of workers' compensation injury claims, aggregated to company business. Risk ratios were estimated with multivariable negative binomial regression models. Models were also fit separately to lost-time claims stratified by company size. Results: Business unionisation was associated with a lower lost-time claim incidence (crude risk ratio, CRR=0.69, 95% CI 0.65 to 0.74); adjusted risk ratio, ARR=0.75, 95% CI 0.71 to 0.80). In subgroup analyses, the magnitude of the ARR declined as company size decreased and was not statistically significant for the smallest-sized companies of =4 full-time equivalent employees. Unionisation was associated (positively) with the incidence of no-lost-time claims in a crude model, but not in an adjusted one (CRR=1.80, 95% CI 1.71 to 1.89; ARR=1.04, 95% CI 0.98 to 1.09). Conclusions: Company unionisation was associated with a lower risk of lost-time workers' compensation injury claims, corroborating a similar study from an earlier time period. The protective effect of unionisation declined as company size decreased. In contrast to the previous study, a positive relationship between company unionisation and no-lost-time claim incidence was not found, due in part to a methodological refinement.