Business activity in U.S. service industries grew in December for the 25th consecutive month, the Institute for Supply Management said Thursday. The pace of growth picked up slightly with the headline Purchasing Managers Index was 52.6, up from 52 in November. The index uses 50 as a break-even point. Above 50 indicates growth. Below 50 indicates a contraction. The critical new-orders index for non-manufacturing businesses rose from 53 to 53.2. The employment index rose from 48.9 to 49.4, meaning the pace of job erosion slowed. The prices index fell from 62.5 to 61.2. In the month, 11 of 18 service industries tracked in the report showed growth, led by retail trade, professional, scientific and technical services, mining, and transportation and warehousing.