A target-date fund makes one powerful promise: choose an approximate retirement year and let the portfolio handle asset allocation and rebalancing. Bill Bengen, known for developing the 4% retirement-withdrawal rule, argues that the resulting portfolios are too conservative. His criticism is useful, but it does not establish that millions of savers have chosen the wrong product. It identifies the information that the product cannot know.
A standard glide path can observe time. It cannot observe a household's pension, spouse's assets, mortgage, desired spending, job security, health costs or capacity to tolerate a severe drawdown. The investor question is therefore not whether target-date funds are categorically good or bad. It is whether an age-based default fits the investor's complete balance sheet—and whether a more customized alternative would actually be maintained.
Default design explains the 81%
Business Insider, republished by Yahoo Finance, reported that 81% of Gen Z participants and 70% of millennials in Fidelity's data held their entire 401(k) balance in target-date funds in the second quarter of 2026. Those figures are striking, but they do not necessarily show that young workers independently compared glide paths and selected one. Target-date funds are widely used as qualified default investment alternatives in workplace plans.
The architecture matters. Automatic enrollment puts contributions into a diversified portfolio without requiring a new employee to select funds, estimate risk tolerance and remember to rebalance. The Department of Labor tells plan fiduciaries to establish a process for comparing funds, understand their investments and fees, and review them periodically. The default is designed to solve an implementation problem, not to certify that one allocation is optimal for every participant.
Fidelity's broader Q2 retirement analysis covers more than 55 million IRA, 401(k) and 403(b) accounts. It reported an average 401(k) savings rate of 14.4%, including employer contributions, and said 81.2% of participants contributed enough to receive their full match. Those behaviors—participating, capturing the match and staying invested—can matter at least as much as fine differences between reasonable asset mixes.
A retirement year is a sparse data input
Target-date funds generally reduce equity exposure as the named year approaches. Yet funds with the same year can follow different routes. A “to retirement” glide path reaches its most conservative point at the target date. A “through retirement” path continues changing for years afterward. The Labor Department notes that strategy, allocation and fees can vary significantly even among funds sharing a date.
This creates a mismatch between a precise-looking label and a coarse input. Two 50-year-olds may expect to retire in 2040 while having entirely different financial exposures. One may have a defined-benefit pension that behaves like a bond; another may rely almost completely on the 401(k). One may own a paid-off home; another may face a large mortgage. The same fund can therefore be conservative relative to one household and aggressive relative to the other.
The SEC's investor bulletin explicitly says that the appropriate fund may differ from the expected retirement year depending on objectives, risk tolerance and other assets. That is not a defect hidden by the product. It is a boundary investors can miss when “set it and forget it” is interpreted literally.
Conservative is relative to the liability
Bengen's case favors substantially more equity exposure than many conventional glide paths. Higher equity weight can raise long-run expected return, which is relevant for a retirement that may last decades. But “too conservative” is not a complete diagnosis without defining the liability the portfolio must fund.
An investor making regular contributions can often endure volatility differently from a retiree drawing cash. Near retirement, an early market loss combined with withdrawals can permanently reduce the capital available for a later recovery—the sequence-of-returns problem. A pension or flexible spending plan can absorb that risk; a household with fixed essential expenses and no outside income may have less room. The same allocation can be rational in one case and fragile in another.
There is also model risk on both sides. A glide path embeds assumptions about future returns, correlations, longevity and participant behavior. Bengen's preferred allocation embeds assumptions too. Neither converts uncertain markets into a guarantee. The most defensible inference from his criticism is that age alone is insufficient for full personalization, not that more equities will necessarily produce a better realized outcome for every saver.
Simplicity is an investment feature
The strongest counterargument to customization is behavioral. A self-built portfolio can be cheaper or more tailored, but it also requires decisions about diversification, rebalancing and risk after large market moves. A theoretically efficient mix that an investor abandons during a sell-off can be worse than a merely adequate fund held consistently.
Target-date funds bundle global diversification, automatic rebalancing and a scheduled risk transition. That package can reduce inertia at enrollment and prevent a portfolio from becoming accidentally concentrated after one asset class outperforms. Convenience is not free—fees and underlying holdings still matter—but it is not empty marketing either. It supplies an operating system for savers who do not want to run a portfolio.
Regulators still see room for clearer information. The Government Accountability Office estimated that target-date assets in defined contribution plans totaled about $2.8 trillion in June 2023 and recommended updated participant and sponsor guidance. As of August 2026, those recommendations remained open, with the Labor Department reporting that it would review them after a related final rule. The unresolved disclosure question supports scrutiny, not blanket rejection.
The useful question comes after the fund name
Evidence that would change the evaluation is household-specific and product-specific. The fund's current equity allocation, its “to” or “through” path, underlying fees and expected allocation at retirement reveal what the label actually contains. Pension income, outside investments, debt and the flexibility of planned withdrawals reveal what role it plays.
If those facts show that the target-date fund creates a material mismatch, the criticism becomes actionable as an analytical conclusion. If they show a diversified, low-cost portfolio aligned with the household's risk capacity—and the realistic alternative is cash, concentration or market timing—automation may be the stronger feature.
Bengen has highlighted a genuine blind spot: a date is not a balance sheet. The right lesson is to look through the label, not to replace one universal rule with another.