Background: In recent decades, the frequency of Medical Only (MO) and Lost Time (LT) workers' compensation claims has decreased, while average severity (medical and indemnity costs) has increased.
Objective: The aim of this study was to compare claim frequency, mix, and severity (cost) over two periods using a claim cohort follow-up method.
Methods: Sixty-two thousand five hundred thirty-three claims during two periods (1999 to 2002 and 2003 to 2006) were followed seven years postinjury. Descriptive analysis and significant testing methods were used to compare claim frequency and costs.
Results: The number of claims per $1 M of premium decreased 50.4% for MO claims and 35.6% for LT claims, consequently increasing the LT claim proportion. The average cost of LT claims did not increase.
Conclusion: The severity increase is attributable to the proportional change in LT and MO claims. While the number of LT claims decreased, the inflation-adjusted average cost of LT claims did not increase.