The number of Americans who signed contracts to buy homes rose in December, marking the fifth increase in six months.

The National Association of Realtors says its index of sales agreements for previously occupied homes rose 2 percent last month. The index posted a 3.1 percent increase in November.

Economists have cautioned that a big reason for the jump is that people are buying foreclosed homes. Still, the increase is likely to give the weak housing market a boost in the first few months of the year, because there’s usually a one- to two-month lag between a sales contract and a completed deal.

Contract signings were up in every region of the country except the West.