The U.S. service sector expanded in March for the 16th straight month, although growth slowed from the previous month's pace, which was the fastest in more than five years.

The Institute for Supply Management, a private trade group, says its index of service-sector activity dropped to 57.3 last month, from 59.7 in February. That's the first drop in seven months. Still, any reading above 50 indicates expansion.

The sector employs about 90 percent of the work force, with a range of industries that include retail, health care, financial services and construction. The index plummeted to 37.6 in November 2008, at the height of the financial crisis.

Measures of new orders and employment also dropped. And respondents expressed concern about rising fuel prices.