Washington ? The number of housing projects builders broke ground on in January declined by the largest amount in nearly a year as bad winter weather played havoc with construction activity.

The Commerce Department reported Wednesday that the number of residential buildings under way dropped to a seasonally adjusted annual rate of 1.90 million units, representing a sharp 7.9 percent drop from December’s stellar pace of 2.07 million units. That had been the best pace since February 1984.

Although economists were predicting a slowdown in January from such lofty levels seen in December, last month’s performance was weaker than the pace of around 2 million units that analysts were forecasting. Still, even with the decline, the pace of residential construction in January was still fairly brisk and was up 4.1 percent from the same month a year ago.

The housing market — throughout the economic slump and the recovery — has been the economy’s shining star, providing a source of support for business growth. Economists predict housing activity will be less of a contributor to growth this year but that the sector will stay healthy.

Home sales reached record high levels in 2003, powered by low mortgage rates that proved too good for buyers to pass up. Sales of both previously-owned homes and new ones should have their second best year ever in 2004 — even with an expected rise in mortgage rates, economists said.

Housing construction in the Midwest plunged by 21 percent in January from the month before to an annual rate of 319,000 units.

Builders work on the roof of a house as temperatures dip into the single digits in Russell Township, Ohio, in this Jan. 7 photo. The number of housing projects started in January declined by the largest amount in nearly a year because of wintry weather.