Fewer Americans signed contracts to buy homes in December, a sign that low mortgage rates have yet to coax more buyers into the market.

The National Association of Realtors says its seasonally adjusted pending home sales index fell 3.7 percent last month to 100.7. The index ended the year below its 2013 average. But the Realtors project sales of existing homes will rebound in 2015 to 5.26 million, a 6.6 percent increase from last year.

Pending sales are a barometer of future purchases. A one- to two-month lag usually exists between a contract and a completed sale.

Lackluster wage growth and rising home prices stifled buying for much of 2014. Those affordability pressures should ease in 2015 due to strong job gains in recent months coupled with falling mortgage rates.