The number of defined benefit plans declined by 18 percent to 35,000 in 2012, after falling 15 percent in 2011, while 401(k) plans dropped for the third year in a row to 484,000, a 4.5 percent fall from 510,000, according to a study released this week by American Investment Planners.

At the same time, the number of 401(k) plans with an employer matching contribution shrunk 4 percent to 356,000. Although the number of 401(k) plans decreased, their assets grew as the S&P 500 rose 13.4 percent and the Nasdaq climbed at a faster 16 percent clip.

At the same time, the nation’s unemployment rate reached its lowest point in four years.

American Investment Planners said many employers are cutting back on their 401(k) match or are eliminating it completely because the match has become less attractive to workers. Many employees don’t contribute enough to their 401(k) plans to get the full employer match and many prefer a cash bonus as opposed to matching contributions since they must pay a penalty if they take money from their 401(k) plan before 59 ½.  

The report by the Jericho, N.Y., firm was based on Department of Labor Form 5500s. All pension plans, including 401(k) and defined-benefit plan sponsors, are required to file the form with the Labor Department annually, except sponsors whose plans have less than $250,000 in assets.