The Economic Cycle Research Institute's weekly leading index measuring the U.S. economy reached a one-and-a-half year high.

"The U.S. economy is firmly set to strengthen in the coming months," said Lakshman Achuthan, managing director of the institute.

In the weekly period ending Jan. 1, the weekly leading index level rose to 131.5. The reading in the prior period was 130.7. However, the index's growth rate was 23.6%, down from 24.0% in the prior period.

The growth rate is derived from a four-week moving average of the level and compared against the previous year's average. As a result, the growth rate and level can move in opposite directions.