Washington: Productivity growth slowed to 1.8 percent and first-time claims for unemployment benefits fell 6,000 last week to 422,000 in the first quarter, the US labour department said on Thursday.

The four-week average of jobless claims, regarded as a more reliable guide to future trends, declined by 14,000 to 425,000.  The number of people receiving state unemployment benefits during the week that ended May 21 remained stable at 3.71 million. 

Nearly four million other people continued to collect payments under a special federal programme adopted in the face of the worst economic slump since the Great Depression. 

The official US unemployment rate stands at nine percent. 

In a separate report also released on Thursday, the labour department said the productivity of US firms climbed 1.8 percent in the first quarter, compared with an advance of 2.9 percent in the final three months of 2010. 

Unit labor costs, meanwhile, climbed at an annualised rate of 0.7 percent in the January-March period after falling 2.8 percent in the fourth quarter of last year. 

Real output expanded 3.2 percent in the first quarter of 2011, the labour department said.