WASHINGTON – Fewer Americans than forecast filed first-time claims for unemployment insurance payments last week, reflecting the volatility of applications during the annual auto-plant retooling period.

Applications for jobless benefits decreased by 26,000 in the week ended July 7 to 350,000, the fewest since March 2008, Labor Department figures showed Thursday. Economists forecast 372,000 claims, according to the median estimate in a Bloomberg News survey. Last week’s distortion is likely to unwind slowly over coming weeks, a Labor Department spokesman said.

Automakers including Chrysler, Ford and Nissan are keeping more plants than normal open during this time of year to fulfill demand and replenish inventories. For that reason, it may take time to determine if the labor market is making any progress.

Chrysler announced May 2 that three U.S. plants would skip normally scheduled two-week midyear shutdowns to meet increased demand. Factories in Detroit and Belvidere, Ill., and a parts factory in Toledo, Ohio, are staying open. Two more plants are shutting for one week instead of two, according to Auburn Hills, Mich.-based Chrysler.

Dearborn, Mich.-based Ford said May 8 it would boost production by about 40,000 vehicles by idling 13 plants for one week instead of two as part of the company’s annual summer shutdown.

Nissan is also among automakers averting shutdowns. The Yokohama, Japan-based automaker plans to boost hours, add shifts or increase payrolls at plants in Tennessee and Mississippi, “to really have the supply catch up with demand,” Bill Krueger, Nissan’s vice chairman of the Americas, said in a July 6 telephone interview.