Direct answer: When evaluating a mutual fund or ETF, the most important factors are cost (expense ratio plus trading costs), the index or strategy it tracks, tax efficiency, and liquidity. For passive funds tracking the same index, cost differences are almost entirely predictive of performance differences over time. For active funds, evaluate the strategy's edge and fee justification.
Checklist: Evaluating a Mutual Fund or ETF
Key Takeaways
- Expense ratio is the most persistent predictor of relative performance for passive funds tracking the same benchmark.
- For ETFs, also check bid-ask spread and average daily volume; illiquid ETFs have hidden trading costs that dwarf expense ratio differences.
- Tracking error (how closely the fund matches its index) matters for passive funds; high tracking error on a passive fund usually signals securities lending shortfalls or excessive sampling.
- Active funds require evaluating the strategy's edge, manager tenure, and whether alpha has persisted after adjusting for known factor exposures.
Cost Analysis
The total cost of ownership for a fund includes the expense ratio plus trading costs. For mutual funds, the expense ratio is the all-in annual cost. For ETFs, add the bid-ask spread (half the spread is paid on entry and half on exit) and any commission. A $10,000 position in an ETF with a 0.05% bid-ask spread costs $5 to buy and $5 to sell, equivalent to a 0.1% round-trip cost. For long-term buy-and-hold investors this is trivial; for frequent traders it matters more.
Index or Strategy Evaluation
For passive funds: what index does it track, and how is that index constructed? Market-cap-weighted, equal-weighted, factor-weighted, and fundamentally-weighted indexes all behave differently over time. Verify that the fund actually holds a complete or representative sample of its stated benchmark, not a different index with a similar name. For active funds: what is the stated strategy, what market inefficiency does it exploit, and what is the evidence it has worked net of fees?
Tracking Error and Tracking Difference
Tracking error measures volatility of the fund's return versus the benchmark; tracking difference measures the cumulative gap. A well-run passive fund should have tracking difference close to (often below) its expense ratio, as securities lending income can offset costs. Persistent positive tracking difference (fund lags benchmark by more than its expense ratio) is a red flag for passive funds and usually means poor execution, high internal trading costs, or excessive cash drag.
Tax Efficiency
ETFs are generally more tax-efficient than mutual funds for taxable accounts because the creation-redemption mechanism allows appreciated securities to exit without a taxable event. Mutual funds must sell securities to meet redemptions, potentially distributing capital gains to all shareholders. Check whether the fund has made capital gain distributions in the past five years. Index funds with low turnover are the most tax-efficient. Bond funds generate ordinary income regardless of structure.
Liquidity and AUM
For ETFs, low average daily volume can make large purchases or sales costly. As a rough rule, if your trade is more than 1% of average daily dollar volume, you may move the market and should use limit orders. For mutual funds, verify whether the fund has redemption fees or gates for large withdrawals. For less common asset classes (international small cap, niche sectors), always check liquidity before committing significant capital.
Manager and Strategy Continuity
For active funds, verify manager tenure. A fund's 10-year track record is largely irrelevant if the manager who produced it left three years ago. Check whether the current strategy matches the prospectus description. For passive funds, confirm the fund manager (Vanguard, iShares, State Street, Schwab, Fidelity) has a track record of maintaining low costs and tight index tracking across their other funds.
Frequently Asked Questions
Should I choose an ETF or a mutual fund for the same index?
For taxable accounts, ETFs are typically more tax-efficient and have slightly lower or equivalent expense ratios. For retirement accounts where tax efficiency is irrelevant, both are valid. ETFs require a brokerage account and trade at market prices; some mutual funds (like Vanguard's) can be purchased at NAV with no trading spread directly through the fund company. The difference is small for most investors, so cost and convenience should drive the decision.
What expense ratio is too high?
For broad domestic equity index funds, expense ratios above 0.10% are high relative to what is available (many are 0.03% or lower). For international equity, 0.10 to 0.20% is reasonable. For active strategies, 0.50% is the upper threshold for most categories; funds above 1.0% annually need to demonstrate convincing evidence of after-fee alpha to justify the cost. Bond index funds should be under 0.10% for domestic and under 0.25% for international.
What is tracking difference and why does it matter?
Tracking difference is the cumulative gap between the fund's total return and the index's total return over a period (often one year). A fund with a 0.05% expense ratio and 0.03% tracking difference is actually outperforming its index by 0.02%, likely from securities lending income. A fund with a 0.05% expense ratio and 0.15% tracking difference is underperforming by 0.10% beyond its stated cost, which signals a hidden friction investors should investigate.