Prior to this year's increase, the report says, claim-frequency rates had fallen more than 56 percent, at an average decrease of over 4 percent a year.

The report says that “a number of recession-related factors may have put upward pressure on the [Accident Year] AY 2010 frequency measure, including an increase in new hires as the recovery began to take hold and a possible influx of small lost-time claims that may have been medical-only claims in previous years.”

There was no change in indemnity and medical average costs per lost-time claim for the year, the report says.

Among some of the economic reasons given for the increase:

• A modest increase in the job market of new hires can translate into increased frequency as new hires tend to have higher claim frequency over long-term workers.
• Workers who put off filing workers' comp claims may now be filing those claims as the economy improves as fears that they could lose their jobs diminish.
• There is evidence that small lost-time claims rose because there were less available light-duty jobs available. In the past, those claims would have been classified medical-only claims. NCCI says it is researching the issue further.