(Reuters) - Contracts to buy U.S. previously owned homes fell for a third straight month in November as an acute shortage of properties pushed up prices, though the housing market remains supported by record-low mortgage rates. The National Association of Realtors said on Wednesday its Pending Home Sales Index, based on contracts signed last month, fell 2.6% last month to 125.7. Economists polled by Reuters had forecast pending home contracts, which become sales after a month or two, would be unchanged in November from the month before. Compared with a year ago, pending home sales jumped 16.4% in November. Sales of existing homes have slackened recently, declining in November for the first time in six months. The housing market is being driven by record low mortgage rates. The COVID-19 pandemic, which has seen at least 21% of the labor force working from home, has led to a migration from city centers to suburbs and other low-density areas as Americans seek out more spacious accommodation for home offices and schools. The coronavirus-triggered recession, which started in February, has disproportionately affected lower-wage earners. At least 20 million people are on unemployment benefits. The 30-year fixed mortgage rate is around an average 2.86%, according to the most recent data from the Mortgage Bankers Association. Housing supply has failed to keep up with demand, boosting home prices out of the reach of many first-time buyers, despite builders ramping up construction. Though homebuilder confidence is at historic highs, builders have complained about shortages of land and materials. Pending home sales declined in all four regions. They fell 1.1% in the South, 4.7% in the West, 3.3% in the Northeast, and 3.1% in the Midwest.