The U.S. service sector got 2007 off to a positive start, and grew more quickly in January than it did in December.

A report released today from the Institute for Supply Management said that the private research group’s nonmanufacturing index stood at 59.0 for the first month of the year, after the revised 56.7 seen in December.

The index, which mainly consists of service-related companies, was above the 57.0 economists had expected to see. Readings over 50 indicate growing activity and describe the breadth of that change. The January reading was the best since May.

“Members’ comments in January are mostly positive concerning current business conditions,” said Anthony Nieves, who directs the service-sector survey for the ISM. He added that “the overall indication in January is continued economic growth in the nonmanufacturing sector at a faster pace than in December.”

In the report, the ISM said that its nonmanufacturing price index indicated that inflation grew more slowly, with January’s reading at 55.2, compared with a revised 59.7 for December. The group’s employment index was 51.7, down from December’s revised 53.2. The ISM nonmanufacturing new orders index for January was 55.4, compared with a revised 55.6 in December.