The sluggish economy continues to cut into the online job market, the Conference Board reported this week.

Last month the number of job openings posted online dropped by 13 percent from the same period last year to 3.8 million, according to the New York-based private research group. Only 2.7 million new job ads were posted in May, with the rest held over from April. On average, there were 2.5 online job postings last month for every 100 people in the labor force, the report said.

The overall number of new jobs has fallen nationwide in the past year. In May, Wyoming, Maryland and Delaware reported the lowest supply-demand rate between the number of unemployed residents and the number of advertised vacancies, while Alaska reported the highest rate of job openings.

"May shows a slight recovery from the large April decline, but overall the number of online advertised vacancies has been on a downward trend for the past several months," Gad Levanon, a Conference Board economist, said in a statement. He said the demand for labor will likely be sluggish over the summer.