Picture the 401(k) allocation you chose sometime in 2022. Maybe it was 60% stocks and 40% bonds, a textbook moderate mix. You picked it during a rough stretch, it felt right, and you moved on with your life. Three and a half years later, that portfolio has quietly rewritten itself. The S&P 500 surged more than 60% from its October 2022 low through late 2024, then continued climbing into 2025. The broad U.S. bond market, measured by the Bloomberg U.S. Aggregate Bond Index, barely recovered its 2022 losses over the same period. Run the math, and a 60/40 portfolio set in early 2022 likely sits somewhere near 72/28 or 75/25 today, depending on the specific funds. That is not a moderate allocation anymore. That is an aggressive one, and most people who own it have no idea it shifted.
The good news: nearly every major 401(k) plan now offers a rebalancing tool on its website or app, and using it typically takes less than a minute. The bad news: almost nobody does.
Why portfolios drift faster than people expect
Rebalancing is not about predicting where markets go next. It is about maintaining the level of risk you originally chose. When stocks outperform bonds over a sustained stretch, the equity slice of a portfolio grows as a share of the whole. A worker who picked 60/40 because it matched a moderate risk tolerance never signed up for 75/25, yet that is roughly where market math has pushed many accounts since early 2022.
The drift works in reverse, too. Workers who panicked during the 2022 sell-off and moved heavily into bond funds locked in losses near the bottom, then missed the equity recovery. Their accounts may now be far more conservative than intended, which carries its own long-term cost: not growing enough to fund retirement.
Neither scenario reflects a deliberate choice. Both reflect inertia, and inertia is the default setting for most retirement savers. Behavioral economists Brigitte Madrian and Dennis Shea documented this pattern in landmark research on automatic enrollment: once people land on a contribution rate or investment mix, they tend to stay put for years, regardless of how much conditions change.
What federal rules actually guarantee
The legal framework behind your 401(k) creates two distinct groups of savers, and the protections differ sharply.
Default investors. Workers who never chose their own funds are typically placed into a qualified default investment alternative, or QDIA. Under Department of Labor guidance on default investments, these are usually target-date funds that automatically rebalance on a set schedule, gradually shifting from stocks to bonds as the target retirement year approaches. If you were auto-enrolled and never changed anything, your portfolio is likely being rebalanced for you. Vanguard’s 2024 “How America Saves” report, which analyzed plan-year 2023 data, found that roughly 64% of new contributions flowed into target-date funds. That suggests a large share of participants do benefit from automatic rebalancing, whether they realize it or not.
Self-directed investors. Anyone who logged in and built a custom allocation, even once, falls into a different category. Under ERISA section 404(c), the plan earns liability protection as long as it gives participants enough information and a genuine opportunity to manage their investments. That means access to prospectuses, fee disclosures, and performance data. But the plan is not required to send you a warning when your allocation drifts 10 or 15 percentage points from where you set it. You chose to drive; the plan just has to make sure the steering wheel works.
A worker who picked funds during a volatile stretch in 2022 and then stopped paying attention is, legally speaking, in full control of an allocation that may no longer match their goals. No one is coming to tap you on the shoulder.
The “two clicks” rebalance, step by step
Major recordkeepers, including Fidelity, Vanguard, Empower, and Schwab, have built rebalancing directly into their participant dashboards. The typical process is simpler than most people assume:
- Log in and find the rebalance option. On most platforms, it appears on the main account overview page or under an “Investments” or “Manage” tab. Labels vary: “Rebalance,” “Realign,” or “Reset allocation” are common.
- Review and confirm. The tool displays your current allocation alongside your stated target (or lets you set a new one). It shows the proposed trades. You hit confirm.
That is the whole process. Because 401(k) accounts are tax-deferred, selling appreciated stock funds to buy bond funds inside the plan triggers no capital gains tax. There is no 1099, no extra tax form, no penalty. The friction is almost entirely psychological, not financial.
Some plans also offer an automatic rebalancing feature that executes the reset on a quarterly or annual schedule. If your plan has it, turning it on once eliminates the need to remember. Check your plan’s settings page or call the number on your statement to ask. Academic research on rebalancing frequency, including work published by Vanguard’s investment strategy group, generally finds that annual or semiannual rebalancing captures most of the risk-management benefit without excessive trading.
What the data shows about who actually rebalances
No federal agency tracks how many individual 401(k) participants rebalance after a major market move. The Department of Labor publishes rules and enforcement actions, not login analytics. What we have instead are proprietary snapshots from the large recordkeepers, and the picture they paint is consistent.
Vanguard’s 2024 report found that only about 5% of participants made any exchange at all during 2023. That figure includes people who changed funds for any reason, not just rebalancing. The actual share who deliberately rebalanced is almost certainly smaller. Fidelity’s quarterly retirement analyses have shown similar patterns: the vast majority of participants make zero changes in a given year, even after sharp market swings.
These reports each cover only one firm’s book of business, and methodologies vary. But the pattern holds across providers and across years. Most self-directed 401(k) investors do not adjust their holdings. The behavioral research on inertia in retirement accounts, stretching back to Madrian and Shea’s early work and reinforced by subsequent studies, supports the same conclusion: people stick with whatever they last chose, often for far longer than they intend to.
Three questions to ask yourself before July
If you have not logged into your 401(k) since 2022, or even since last year, a short check-in can reveal whether your portfolio still reflects your intentions. Here is what to look for:
1. What is my current stock-to-bond ratio? Compare it to whatever you originally chose. If the gap is more than five percentage points in either direction, drift has done real work on your risk profile. A portfolio that has drifted from 60/40 to 75/25 carries roughly the same volatility as a portfolio that was designed to be aggressive from the start.
2. Am I in a target-date fund or a custom mix? If your entire balance sits in a single target-date fund, rebalancing is handled for you. If you picked individual funds or split between a target-date fund and other holdings, the non-target-date portion is drifting on its own.
3. Does my plan offer automatic rebalancing? If so, turning it on takes the decision off your plate going forward. If not, set a calendar reminder to check at least once a year. Twice is better.
One common worry: “Should I wait to rebalance because the market might keep going up?” That question treats rebalancing as a market call, which it is not. Rebalancing is a risk-management decision. If your allocation has drifted well past your comfort zone, waiting for a better moment is just another form of inertia.
Why five minutes in June 2026 could matter for years
Rebalancing is not exciting. It does not feel like a financial win the way watching a balance climb does. But its purpose is to keep your portfolio aligned with the level of risk you actually want to carry, not the level the market has assigned you through years of uneven returns. The tools exist in almost every plan. The tax cost inside a 401(k) is zero. The only real barrier is logging in.
If your last allocation decision was made during a period when the market looked fundamentally different, and early 2022 qualifies on every measure, spending five minutes on your plan’s website this month could be the single most productive financial task you do all year. The button is there. It has been there. All it needs is a click.
