A measure of future U.S. economic growth dropped in the latest week, while the annualized growth rate also slowed, a research group said on Friday.

The Economic Cycle Research Institute, a New York-based  independent forecasting group, said its Weekly Leading Index  fell to 126.4 in the week ended Dec. 28 from a revised 127.6 the previous week. That was originally reported as 128.3.

The index's annualized growth rate slowed to 4.9 percent from 5.1 percent a week earlier, which was also revised lower from 5.4 percent.