The US four-week moving average of initial claims for unemployment insurance fell last week to 263,250, the lowest level since mid-December 1973. The moving average fell by 2,000 from the previous week’s average, which was revised slightly upward, according to seasonally adjusted numbers released today by the US Department of Labor.

The four-week moving average decreases the volatility of the weekly numbers. Total initial claims for unemployment insurance for the week ended Oct. 17 rose by 3,000 to 259,000 from the previous week’s upwardly revised level, but remained near the lowest level in decades.

No special factors affected this week’s initial claims.

Bloomberg reported claims rose less than the median forecast in its survey of 47 economists, which projected claims would rise to 265,000.

“The level of outright layoffs is very low,” said Thomas Simons, a money-market economist at Jefferies LLC in New York, who projected 260,000 claims. ‘‘There isn’t much fat left to trim” in the labor market.