WASHINGTON (AP) — The pace of Americans signing contracts to buy homes rose for a third straight month in December, raising an index of pending home sales by 0.5 percent.

The National Association of Realtors says its index of pending sales reached 110.1, up from a revised 109.6 in November. The index is now at its highest level since registering 111.3 in March.

More Americans are looking for homes as the economy has improved, though a shrinking supply of properties on the market has made the hunt difficult and driven up prices.

The number of signed contracts rose in the South and West in December but declined in the Northeast and Midwest.

Pending sales contracts are a barometer of future purchases. Sales typically follow a month or two after a signed contract.