How to choose your 401(k) investments: reading the fund menu

Nobody chooses a 401(k) the way they choose a broker. The employer picks the plan, the recordkeeper, and the fund lineup; the tax treatment is set by statute; the only live decisions are how much to contribute and which lines of a fixed menu to fill. That narrows the question usefully. This page is a method for reading the menu: the fee layers, the target-date default, the match arithmetic, the company-stock line, and the exit mechanics, each with dated market data.

The wrapper itself is documented territory this page will not re-teach: 401(k) versus IRA covers the structural comparison, and pre-tax deductions and brackets the entry-side arithmetic. What follows assumes both and starts where they stop: at the plan document.

1. The menu is the decision

A 401(k) is an employer product before it is an investment. The participant inherits a lineup, typically a few dozen funds, chosen by a plan sponsor whose incentives are fiduciary but whose attention is finite. Two plans with identical tax treatment can deliver outcomes tens of thousands of dollars apart over a career, purely through the cost and quality of that lineup. The industry’s own history explains why the menu deserves the attention the tax debate usually absorbs: the 401(k) transferred investment risk and investment choice from employer to employee in a single generation, a shift documented in from pensions to 401(k)s, without transferring any of the analytical apparatus pension boards used. The employee got the menu, not the staff.

Why menus differ so much is itself informative. Lineups accrete: funds added a decade ago under different fee norms persist, share classes with embedded distribution costs linger where nobody has renegotiated, and a sponsor’s periodic review tends to prune the scandalous rather than optimize the mediocre. The direction of travel is favorable, since fee litigation and disclosure rules have pushed averages down for two decades, but the dispersion at any moment remains wide, and dispersion is precisely what a menu reader can exploit. The plan is fixed; the allocation across its lines is not. That asymmetry is the page’s working assumption: everything below concerns the decisions that remain live inside an inherited structure.

The pre-tax versus Roth question, meanwhile, is genuinely important and genuinely elsewhere: Roth or traditional treats it in full. What matters here is a proportionality observation: the tax-timing choice moves outcomes by basis points of lifetime tax rate for most savers, while the difference between a 0.10% index lineup and a 1.5% active-plus-fees lineup moves the terminal balance by double-digit percentages. You do not pick a 401(k); you read the menu you were given.

The proportionality claim is checkable arithmetic, not rhetoric. Over 30 years of $500 monthly contributions at 5% gross, an all-in cost of 0.6% leaves about $373,000 and an all-in cost of 2.0% leaves about $291,000: an $82,000 difference, over a fifth of the larger outcome, produced by nothing except the fee layer (Eco3min calculations, section 7). Few tax-timing scenarios move a median saver’s lifetime outcome by a comparable fraction, and none of them do so with the fee layer’s certainty. The menu is where five-figure amounts change hands quietly.

2. Reading expense ratios inside the menu

The published expense ratio is the visible layer, and the market context for judging it is well documented. In 2024, 401(k) participants invested in equity mutual funds paid 0.26% on average, well below the 0.40% industrywide average, a gap driven by institutional share classes and economies of scale (ICI, The Economics of Providing 401(k) Plans, July 2025). Index equity ETFs averaged 0.14% asset-weighted in 2025 (ICI, March 2026). Against those anchors, a menu whose cheapest S&P 500 option costs 0.05% is normal, and one whose cheapest broad-index fund costs 0.60% is expensive by half a percentage point every year, compounded.

Two structural facts complete the fee picture. First, the plan’s size sets a floor under what any participant can do: total plan cost averages 0.27% in plans above $1 billion in assets and 1.26% in plans below $1 million (Morningstar data via the 401(k) Averages Book, 2025), a small-plan premium that has nothing to do with the funds themselves. Second, the expense ratio is not the only layer: recordkeeping and administrative costs are sometimes charged inside fund expenses, sometimes outside them, which is why two menus with identical tickers can cost differently. The reading method transfers directly from taxable investing, where the brokerage account checklist applies the same layered-cost logic to a chosen rather than inherited account. In practice the menu reads fastest in three passes: locate the broad-index lines and their costs, identify the default and its fee, then price everything else against those two anchors. Most of a lineup’s apparent complexity dissolves once the anchors are set.

Inside the menu, the index-versus-active line deserves one factual observation rather than a doctrine: the dispersion of active outcomes is wide, persistence is weak, and the fee gap is certain. A growth-equity fund at the 90th percentile of cost charges 1.75% or more while the 10th percentile charges 0.60% or less (ICI, 2026); the certain layer is the one a menu reader can act on. Past outperformance in the lineup’s star fund is the least durable information on the sheet.

The perceptual trap is the denominator. A 1% fee reads as small because it is quoted against the balance; quoted against what the balance earns, it is enormous. On a 5% gross year, a 1% all-in cost consumes a fifth of the return; against the real, after-inflation return, the share is larger still. This is the arithmetic behind the compounding gaps in section 7, and it is why the fee line rewards attention out of all proportion to its font size: it is the one number on the fact sheet that applies every year, in every market, with certainty.

3. Target-date funds: the glide path read through the regime

The default deserves its own section because it is where the money actually goes: target-date strategies held $4.8 trillion at the end of 2025, up 20% on the year, with five providers controlling roughly 80% of assets (Morningstar, 2026 Target-Date Landscape). The mechanics are a fund of funds that de-risks on a preset schedule, shifting from equities toward bonds as the target year approaches, at an asset-weighted fee that fell to 0.27% for mutual funds in 2025. As a default for an inattentive saver, the structure is cheap and coherent; regulation made it the default in a strict sense, since target-date funds qualify as default investments for auto-enrolled participants, which is how they came to absorb the contributions of workers who never made an election at all. As an automatic pilot, it embeds one assumption worth naming: that bonds buffer equities.

2022 tested that assumption and the result is on the record: every 2025-vintage target-date fund lost money that year regardless of glide path, because the aggressive rate-hiking cycle sank bonds alongside stocks (Morningstar, Target-Date Landscape 2023). Funds closest to their target date, holding the most bonds, had the least protection precisely when their holders had the least time to recover. The mechanism is duration: a glide path is a bet that the bond leg behaves as it did in the disinflationary decades, documented in the disinflationary regime in detail, and 2022 was the other regime. A saver ten years from their date holds a growing bond leg whose behavior depends on which of those worlds prevails, which is not knowable in advance and is at least observable in the present. The dispersion inside the category is a second reading layer: strategic equity weights for the same vintage have ranged from 20% to 75% across providers (Morningstar, 2022), and the industry splits between “to” glide paths, which stop de-risking at the target date, and “through” paths, which keep shifting for a decade beyond it; in 2022 the most conservative “to” designs lost the least (Morningstar, Landscape 2023). Vehicle structure has shifted too, with collective investment trusts overtaking mutual funds at 54% of target-date assets in 2025, mainly on cost. None of this makes the default wrong; it makes it a strategy with regime exposure, to be read like any other. Today’s regime reading locates the current environment, and the regime performance tool shows what each configuration historically did to the stock-bond pair. The yardstick throughout is purchasing power, not the account statement: thinking in real returns is the difference between a glide path that protected capital and one that merely protected its nominal label.

4. The match comes first

One line of the plan document outranks every fund-selection question: the employer match formula. A match of 50 cents or a dollar per dollar contributed, up to a percentage of salary, is an immediate, contractual return on contribution that no expense ratio discussion touches; contributing below the match cap forgoes compensation that does not come back. The arithmetic, vesting schedules included, is laid out in capturing the employer match, and it belongs before, not after, the menu reading: the order of operations is the one part of 401(k) practice where the numbers speak with one voice. This is a statement about arithmetic; how it maps onto any individual’s budget is theirs to weigh. Two adjacent facts belong to the same reading: vesting schedules determine when matched dollars become property, so the match’s value has a tenure dimension the formula alone hides; and the menu increasingly contains a Roth line, present in 86% of plans covering 96% of participants (Vanguard data, 2024, via ICI), which changes where the tax-timing question from section 1 gets answered without changing its stakes. The match itself is typically indifferent to that choice, since employer contributions land pre-tax either way under prevailing rules.

5. Company stock and the concentration line

Many large plans still carry an employer-stock line, sometimes with a discount or a match paid in shares. The finance is concentration: an employee who holds their retirement capital in the same firm that pays their salary has stacked two exposures on one issuer, and the historical record contains the canonical episode, Enron, where employees lost employment and retirement savings in the same event. Nothing about a specific employer’s stock is predictable from this page; what is documentable is the structure, a doubled exposure that no diversified fund in the same menu carries. Post-Enron reforms improved diversification rights, but the line item still requires the holder, not the plan, to notice the stacking.

The behavioral pull runs the other way, which is why the line persists. Familiarity reads as knowledge: an employee who understands their firm’s products feels informed about its stock, and a discount or share-paid match frames accumulation as loyalty rather than exposure. None of that changes the structure. The information an insider legally has does not diversify anything, and the historical record’s lesson is not that employers fail often, but that when one does, the two losses arrive together, at the moment the household can least absorb them. Reading the line means asking one question of the statement: what share of the balance sits in the employer’s ticker, counting matched shares. The answer is a number, and unlike most numbers in this domain it has no market view attached; it is pure structure.

6. Leaving the plan: rollover mechanics

The menu is inherited, but it is not permanent. At separation, balances can move: to the new employer’s plan, to an IRA, or, at a cost, out of the tax shelter entirely. The mechanics are procedural and the failure modes are documented: cashing out a small balance triggers ordinary tax plus, before 59\u00bd, the penalty regime detailed in early withdrawal rules. Small balances add a procedural wrinkle: below statutory thresholds, plans can force out departed employees’ accounts, and an unattended force-out can land in a cash-equivalent default whose real return is negative. A rollover, executed trustee-to-trustee, preserves the shelter and, in the IRA direction, replaces the inherited menu with an open one, at the price of losing plan-specific features. The comparison between sheltered and open accounts, fees included, is the territory of tax-advantaged versus taxable accounts; the point here is narrower: the moment of leaving an employer is the one moment the menu itself becomes a choice.

The open menu is not automatically the cheaper one, and the data cut against the reflexive rollover. ICI’s fee research finds that 401(k) investors incur lower average mutual fund expense ratios than IRA investors, largely because plans aggregate institutional scale a retail account cannot reach. A worker leaving a billion-dollar plan with a 0.03% index core for a retail IRA has widened their choice set and raised their floor cost simultaneously; a worker leaving a sub-million-dollar plan carrying the small-plan premium has done the reverse. The rollover question is therefore a menu-versus-menu comparison, and the reading method of section 2 applies unchanged on both sides of it.

7. Fees compounded over 25 years

The simulator below makes the fee layer concrete. It compounds a monthly contribution over a chosen horizon under two fee structures: lineup A at a fixed low-cost reference of 0.6% a year all-in, and lineup B at a fee level you set between 0.5% and 3.5%. The gross return assumption, 5% a year before costs, is identical on both branches and is an illustration parameter, not a forecast; what the tool isolates is the only certain difference between the branches, the fees. Read the gap line, not the totals: the totals depend on the return assumption, while the gap’s share of the final balance is driven almost entirely by the fee spread and the horizon, which is the part of the outcome the menu reader controls. Everything displayed is an illustration of compounding arithmetic on stated assumptions, not a projection of any fund’s future performance; the section 1 example ($82,000 of gap on $500 a month over 30 years) is one point of this same surface.

8. FAQ

What fees stack inside a 401(k) menu?

Three layers: the expense ratios of the funds themselves (0.26% on average for 401(k) equity fund investors in 2024, per ICI); plan administration and recordkeeping, charged inside or alongside fund expenses; and, in smaller plans, a size premium that pushes total cost toward 1.26% on average for plans under $1 million (Morningstar data). The visible expense ratio is therefore a floor, not the total. The plan’s annual fee disclosure, which sponsors must provide, is the document that reconciles the layers into what a participant actually pays.

How does a target-date fund glide path work?

A target-date fund holds other funds and shifts the mix from equities toward bonds on a preset schedule anchored to the target retirement year. The design assumes bonds cushion equities; 2022 showed the assumption is regime-dependent, when every 2025-vintage fund lost money as rates rose (Morningstar). Fees have fallen to 0.27% asset-weighted for mutual funds (2025), making cost a weaker objection than the embedded duration bet. Two funds with the same target year can also hold very different equity weights, so the vintage label describes a schedule, not a risk level.

What does the employer match change arithmetically?

It is a contractual addition to contributions, typically 50% to 100% of what the employee puts in up to a salary-percentage cap. Below the cap, each unmatched dollar forgoes its match permanently; no fund-selection decision inside the menu has a comparable arithmetic effect. Vesting schedules can defer ownership of matched amounts, which is a reason to read the plan document, not a reason the match matters less.

What risks come with company stock in a 401(k)?

Concentration stacked on employment: salary and retirement capital exposed to the same issuer, so one corporate failure hits both, the pattern the Enron episode made canonical. Diversified funds in the same menu do not carry the stacking. Reforms since have strengthened the right to diversify out of employer shares; the structural exposure remains wherever the line is held. For the behavioral side of first portfolios, investing basics for beginners covers the ground.

How does a rollover work when leaving an employer?

Executed trustee-to-trustee, a rollover moves the balance to a new plan or an IRA without tax; taking the cash instead triggers ordinary income tax plus, generally before 59\u00bd, a 10% penalty. The choice interacts with decumulation questions that have their own documented territory: annuity or lump sum for the payout structure, and the 4 percent rule examined for what withdrawal-rate research does and does not establish.

9. The menu you were given, read in order

The reading order this page defends is arithmetic first, fees second, structure third: capture the match, find the cheapest broad-index core, read the default’s glide path as a regime bet rather than a guarantee, and treat company stock as the concentration it is. None of that requires predicting markets; all of it is legible in the plan document and the fund fact sheets. The environment the menu operates in is the remaining layer: matching vehicles to the rate cycle connects the account to the regime, and building resilient portfolios places the 401(k) inside the allocation it exists to serve. You do not pick a 401(k); you read the menu you were given, and the reading is learnable. It takes one plan document, two fact sheets and an hour, which is a favorable exchange rate against a five-figure compounding gap.

Last updated: 8 July 2026

Last updated — 8 July 2026