Jan. 8 (Bloomberg) — Companies added more workers than projected in December as U.S. employers grew more optimistic about the prospects for demand, a private report based on payrolls showed today.

The 238,000 increase in employment was the biggest since November 2012 and followed a revised 229,000 gain in November that was stronger than initially estimated, according to the ADP Research Institute in Roseland, New Jersey. The December tally exceeded the most optimistic forecast in a Bloomberg survey in which the median projection called for a 200,000 advance.

A pickup in hiring coupled with wage gains are helping to spur faster growth in the consumer purchases that make up almost 70 percent of the economy. A Labor Department report this week may show private payrolls rose by 197,000 last month, according to the Bloomberg survey median.