NEW YORK (TheStreet) -- The number of workers investing in 401(k) retirement plans administered by Wells Fargo (WFC) has risen 13% in the past four years. Their average account balance has grown even more: It's up 33%, at $93,000.
"I get very excited when I see the percentage of employees enrolling in plans ticking up over the last four years because it tells me people understand that participation in their workplace retirement plan is vital," Joe Ready, head of Wells Fargo's Institutional Retirement and Trust, said in a statement.
Altogether, the San Francisco-based bank administers plans for about 3.8 million workers at U.S. companies. The recent volume growth reflects an increase in employers enrolling workers automatically -- 40% do so now, compared with 30% in 2011 -- as well as heightened interest in retirement plans among Millennials, Wells Fargo said. Numbering 92 million, the generation born between 1980 and 2000 is the biggest in U.S. history.
About 55% of Millennial workers eligible for a Wells Fargo plan are investing in it now, up from 45% in 2011. The bank also saw growth in investment by new hires and workers making less than $40,000 a year.
"We know that systematic, pre-tax savings and investing works," Ready said. "The first critical step along that journey is to get people in the plan. To see such gains among people who are historically the hardest to get saving for retirement is also quite encouraging."
Nationwide, the amount invested in 401(k)s and similar pension plans climbed 46% over the past four years to $5.52 trillion, according to data from the Federal Reserve. Household net worth increased about 33% to $84.9 trillion.
Despite their increased interest in saving, Millennials still lag in the amount of pay they devote to it. Only 28% of them contribute at least 10% of their salary, lagging behind Gen X-ers at 35% and Baby Boomers at 45%.
"What we really need to see is a more robust increase in how much people are saving," Ready said. "The reality is that people need to save their way to retirement. This is true for all generations, and especially so for the younger population that has time on its side and can take advantage of the compounding effect of time."
Millennials, many of whom came of age during the financial crisis and its aftermath, tend to have more diversified portfolios. Some 82% of them split investment between at least two equity funds and one fixed-income fund, with no more than a fifth of their contributions allocated to employer stock. That outpaces Gen X-ers and Baby Boomers at 78% and 75%, respectively.
Millennials are "the most diversified generation, and are making the biggest gains," Ready wrote. They're particularly fond of Roth 401(k) plans, which allow participants to invest after-tax earnings and make tax-free withdrawals upon retirement. About 16% of Millennials use Roth plans, compared with 11% of Gen X-ers and 7% of Baby Boomers, Wells Fargo said.
Wells Fargo also found that women are slightly more likely to participate in an employer's 401(k) retirement plan than men, at 65% versus 62%, although they tend to invest smaller portions of their paychecks.