The National Retail Federation, the nation's largest retail trade group, says that holiday sales increased a lower-than-expected 2.9 percent as worries about the trade war with China, the government shutdown and stock market turmoil dampened shopper spending in December.

The figures, released Thursday, come after the Commerce Department announced weak December retail sales data that had been delayed by nearly a month because of the government shutdown. The group and other analysts are questioning whether the shutdown and resulting delay in collecting the data had made the results less reliable.

The numbers, which exclude automobile dealers, gas stations and restaurants, fell short of the trade group's forecast for the November and December period combined to increase anywhere from 4.3 percent to 4.8 percent.