WASHINGTON—Contracts to buy U.S. previously owned homes fell for a second straight month in December amid record low inventory. The National Association of Realtors (NAR) said on Thursday its Pending Home Sales Index, based on signed contracts, dropped 3.8 percent last month to 117.7. Pending home sales fell in all four regions. Economists polled by Reuters had forecast contracts, which become sales after a month or two, dipping 0.2 percent. Pending home sales decreased 6.9 percent in December on a year-on-year basis. “Pending home sales faded toward the end of 2021, as a diminished housing supply offered consumers very few options,” said Lawrence Yun, NAR chief economist. An acute shortage of previously owned homes is hampering sales. Despite rising mortgage rates, which together with high home prices are reducing affordability, demand for housing is likely to remain strong this year. “The market will likely endure a minor reduction in sales …