Today, approximately one-in-five Americans 65 and older are working or looking for jobs, according to the U.S. Bureau of Labor Statistics.

The percentage of Americans working after turning 65 is expected to increase to 23.3% in 2028, according to recent analysis from the Pew Charitable Trusts, which reports the workforce participation rate for the same age group was just 12% in 1998.

About half of the 9 million working senior citizens in the U.S. are employed in retail, health care, business services or education, according to Pew’s analysis. While some of the highest-paying jobs held by seniors are at colleges and universities, where their average salary is over $93,000 a year, more than 165,000 working seniors are employed in grocery stores where they earn an average of $31,000 a year.

To some extent, the rise of older workers is displacing younger ones, writes Pew. "The Bureau of Labor Statistics noted that as older people return to the job market, younger people 16 to 24 are not seeking jobs as much as they once did -- partly because they’re staying in school, as the long-term benefits of college degrees become more obvious. But part of the reason is that older workers now hold the kinds of jobs that entry-level workers once did."

Pew notes that some of the rise in senior employment may be due to Social Security sticker shock, when older Americans realize that their Social Security benefits fall far short of their living expenses. Currently, benefits for those who claim Social Security at age 62 max out at $2,209 a month, while those filing at age 70 will find that their benefits max out at $3,770 a month.

Looking at senior citizen workforce participation on a state-by-state basis, there was some geographic variation, though the share of people over 65 with jobs increased in 36 states over the past five years. Most New England states, for example, had high rates of senior workforce participation, led by Vermont, where 26% of the over-65 population is currently employed. Senior workforce participation tends to be lower in the southeastern states, particularly Mississippi and Kentucky, where just 14% of those 65 and older reported having jobs.

Looking more closely, Pew says that seniors in high-cost-of-living areas like Loudoun County, Va., a Washington, D.C. suburb, are feeling more pressure to hold jobs -- more than a quarter of the people age 65 and older in Loudoun County hold jobs.

Pew also associated the growth in senior workforce participation with the decline in defined-benefit pension plans.

As a result, some states are “scrambling” to fund job-training programs for seniors, according to Pew, especially in Colorado, Minnesota and Hawaii, where the employment rate among older workers is increasing the fastest.

Pew’s report was based on an analysis of 2018 U.S. Bureau of Labor Statistics data and recent census data.