The U.S. non-manufacturing sector grew in December at it fastest pace in more than 4 years, according to an industry report released on Wednesday.

The Institute for Supply Management said its index of national services activity rose to 57.1 in December from 55 in November, The median forecast of 51 economists surveyed by Reuters was for a reading of 55.6.

A reading below 50 indicates contraction in the non-manufacturing sector, while a number above 50 means expansion.

The reading was its highest since May 2006 when the service sector grew at 57.2.

The reports employment component fell to 50.5, while new orders, a leading indicator, jumped to 63.