Public employees represent 15% of the U.S. workforce, yet control 37% of employer-sponsored retirement plan assets, according to Spectrem Group.

The findings-based on 2009 data contained in Spectrem's annual Retirement Markets Insights study-include state and local government employees, but exclude federal employees, the Lake Forest, Ill.-based market research firm reported.

"I think it provides an interesting perspective given the current debate over public employee benefits going on in many states right now," said Gerry O'Connor, the firm's director and head of research.

Based on the U.S. Census Bureau's 2011 Statistical Abstract, the total U.S. workforce, excluding federal government employees, was 128 million in 2009, with 19.7 million working for state and local governments and 108.3 million in the private sector.

Employee-sponsored retirement plans held $9.3 trillion in assets in 2009, with public sector employees accounting for $3.4 trillion, or 36.7%, and private sector employees holding the other $5.9 trillion, or 63.3%.

That means the average public employee holds about three times the employer-sponsored retirement plan assets as an employee in private industry.

Sixty-eight percent of public retirement assets were in defined-benefit plans, while only 32% were in defined-contribution plans. Conversely, only 37% of private retirement assets were in defined-benefit plans, with 63% in defined-contribution plans. More than 40% of private sector retirement plans were held in 401k plans, according to Spectrem.