A minority of industrial-back-sprain claimants account for most of the cost of industrial back sprain: those whose disability persists into "chronicity", which is defined as 90 days or more off work. The data in this study demonstrate the effects of socioeconomic factors on chronicity. This analysis is based on State of Washington industrial insurance claims for back sprain. For both men and women, three socioeconomic factors significantly affect the risk of chronicity: age, wage, and the family status of being either widowed or divorced with no children. In addition, the Nam-Powers Socioeconomic Index is significant for men. Wage compensation ratio cannot be shown to be a factor in chronicity.