Economic activity in the U.S. service sector continued to post growth in May, and there was good news for employment, according to the Institute for Supply Management.

The institute's nonmanufacturing index's May reading of 55.4 was unchanged from March and April. Index readings of more than 50 indicate expansion.

However, the employment portion of the index posted a growth reading in May of 50.4 -- the first growth reading in 28 months.