Business activity in the non-manufacturing sector of the U.S. economy expanded in August, though many executives are concerned about rising energy costs, according to a survey of business managers.

The Institute for Supply Management, which surveyed about 370 businesses throughout the U.S., said its non-manufacturing index rose to 65% in August from July’s 60.5%.

A reading above 50 indicates the sector is expanding; below 50 indicates manufacturing activity is shrinking. The index is compiled from a survey of purchasing executives in over 62 industries across the country.