Fewer workers are being covered by employer-based retirement plans, a trend that has been continuing for at least a decade, says an Employee Benefit Research Institute (EBRI) review of U.S. Census data.

Among those most likely to be covered by a retirement plan-full-time, full-year wage and salary employees-54.4% were covered by a defined benefit or defined contribution plan last year, a decrease of 6 percentage points from the 60.4% high of 1999. When considering all workers, 39.6% had some kind of retirement plan last year, a drop of 5% from the 44.4% enrolled a decade ago. It is the first time the percentage has dropped below 40% in 15 years.

Because of economic pressures on businesses and employers, the number of employers offering retirement benefits is following a similar downward spiral, according to the census data. Last year 61.18% offered full-time workers retirement benefits, a decrease of 8% from the high of 69.4% in 1999.

EBRI notes the downward trend in retirement plan participation is likely to continue this year since the unemployment rate has remained higher than it was before the economic downturn of 2008, and because many large private-sector employers have frozen their traditional defined-benefit pension plans.

Now, more older workers are covered than younger ones; Hispanics are the least likely to be covered; and workers in the South, West and Southwest have the lowest participation rates.

"The (long-term) trend has important implications for workers, since having more opportunities to participate in an employment-based retirement plan greatly increases the amount of money a retiree is likely to have in retirement," says Craig Copeland, senior research associate at EBRI and author of the census analysis.

"Any trend toward non-participation is not good. Older workers will have to work longer or do without," Copeland adds. "Younger workers who do not participate now will make it harder for themselves in the future. Any (level of) participation can make all the difference going forward."