Assets in 401(k) plans reached a record $3.075 trillion in 2010, according to the latest Marketplace Update report from the Society of Professional Asset-Managers and Record Keepers (SPARK) and The SPARK Institute.

"Assets in 401(k) plans increased approximately 13 percent in 2010 due to favorable investment results and net cash flow higher than recent trend levels," said Bob Wuelfing, President of RG Wuelfing & Associates, Inc., which prepared the report. "Strong performance across all equity sectors, especially the U.S. market over the second half of 2010, coupled with positive returns in the bond markets, helped push total retirement market assets to an estimated $16 trillion by year-end, 2010." 

Wuelfing noted that there were 536,000 401(k) plans, covering more than 74 million workers in the U.S. in 2010, compared with 510,500 plans and 73.4 million participants reported in 2009.