A measure of future U.S. economic growth strengthened in the latest week to its highest in a year and a half, while the annualized growth rate edged up, a research group said on Friday.

The Economic Cycle Research Institute, a New York-based  independent forecasting group, said its Weekly Leading Index  rose to 128.3 in the week ended Jan. 4, its best showing since August 2011, from a revised 126.6 the previous week. That was originally reported as 126.4.

The index's annualized growth rate was 5.1 percent compared with 5.0 percent a week earlier and an initially reported rate of 4.9 percent.