WASHINGTON (AP) — The number of Americans who signed contracts to buy homes fell in December after hitting the highest level in a year and a half.

The National Association of Realtors says its index of sales agreements fell 3.5 percent last month to a reading of 96.6. That's down from November's reading of 100.1.

But the reading is still the second highest since April 2010, the last month that buyers could qualify for a federal home-buying tax credit.

A reading of 100 is considered healthy.

Contract signings typically indicate where the housing market is headed. There's a one- to two-month lag between a signed contract and a completed deal. But in recent months, a growing number of buyers have cancelled contracts at the last minute.