A measure of job prospects in the U.S. rose in December to the highest level since July 2008, a sign the labor market sustained gains as the year ended.

The Conference Board’s Employment Trends Index increased 0.8 percent to 109.02, the third straight gain, the New York-based private research group said Monday. The prior month’s reading was revised up to 108.19. The measure climbed 3.1 percent from December 2011.

The report follows Labor Department data last week that showed the economy rounded out a third year of job gains with another month of employment growth in December, sending the strongest signal yet that it kept expanding even as lawmakers were struggling to reach a budget agreement to avert fiscal tightening.

“The Employment Trends Index is improving,” Gad Levanon, director of macroeconomic research at the Conference Board, said in a statement. “However, if economic activity continues to expand slowly in the first half of 2013, it would be difficult for employers to maintain the current rate of job growth.”

Payrolls rose by 155,000 last month following a 161,000 gain in November, the Labor Department said on Jan. 4. The jobless rate held at 7.8 percent after the November figure was revised up from a previously reported 7.7 percent. The data also showed bigger-than-projected gains in wages and the workweek that will give households the means to sustain spending, benefiting retailers from Macy’s Inc. to Gap Inc.

Four Increase

The Employment Trends Index aggregates eight labor-market indicators to forecast short-term hiring trends. On average, it can signal a rebound in hiring as little as three months before the fact and can predict job declines six to nine months in advance, the Conference Board said.

Improvements in four of the index’s eight components contributed to the increase in the overall gauge, the report showed. These included fewer first-time claims for unemployment benefits, a decline in those saying jobs were hard to get, and a pickup in industrial production, the report showed.