The latest report by IHS Markit revealed on Monday the seasonally adjusted IHS Markit final U.S. Manufacturing Purchasing Managers’ Index(PMI) rose to 57.1 in December, up from 56.7 in November and slightly up from the earlier released “flash” reading of 56.5. The December reading pointed to the sharpest expansion in factory activity since September 2014.

Economists had forecast the index to stay unrevised at 56.5.

According to the report, the headline figure was pushed higher by severe supply chain disruption in December, which are limiting production capabilities as well as driving producers’ input prices sharply higher. Meanwhile, production and order books continued to grow, albeit with the rates of expansion slowing as a result of rising virus case numbers and related restrictions.