What Is an
Index Fund?
An index fund buys every stock in a market index — like the S&P 500 — and charges a tiny fee for doing so. Historically, that strategy has beaten 90%+ of professional stock-pickers over 20-year windows.
The one-paragraph answer
An index fund is a pool of money from many investors that buys all the stocks in a specific market index in proportion to their market weight. Instead of paying a portfolio manager to pick which stocks will outperform, the fund just buys the index — every stock, every weight. You earn the average return of the entire market (minus a very small fee), which over 20+ year periods has reliably beaten 85-95% of actively managed mutual funds net of their higher fees. The most common indexes tracked are the S&P 500 (largest 500 US companies), the Total US Market, the FTSE 100 (UK), the ASX 200 (Australia), and the TSX 60 (Canada).
How they actually work — the mechanics
Take the S&P 500 as an example. The S&P committee maintains a list of 500 large US companies, ranked by market cap and adjusted for criteria like profitability and float. The committee publishes the exact weights — Apple is currently ~7%, Microsoft ~6%, Nvidia ~6%, Amazon ~3.5%, and so on down to about 0.01% for the smallest constituents.
An S&P 500 index fund (like Vanguard VOO, Fidelity FXAIX, Schwab SWPPX, or iShares IVV) simply buys all 500 stocks in those exact weights. If Apple is 7% of the index, the fund holds 7% of its assets in Apple. When companies enter or leave the index — Tesla joined in 2020, Yahoo was removed in 2017 — the fund mechanically rebalances. There's no judgement involved; it's a rule-following machine. That's why the fees are so low.
Index funds vs actively managed funds
| Feature | Index fund | Active fund |
|---|---|---|
| Strategy | Buy all stocks in an index | Manager picks stocks to beat the index |
| Typical fee (expense ratio) | 0.03–0.20%/yr | 0.50–1.50%/yr |
| Tax efficiency (taxable account) | High — low turnover | Lower — frequent trading triggers capital gains |
| Track record vs benchmark | Matches index minus fees | 85-95% UNDERPERFORM benchmark over 20 yrs (SPIVA) |
| Transparency | Holdings published daily | Holdings often disclosed only quarterly |
| Minimum investment | Often $0-$100 (or 1 share for ETFs) | Often $1,000-$10,000 |
| Best for | Long-term wealth-building, beginners | Niche strategies, high-conviction picks |
What returns can you actually expect?
The honest answer: nominal 8-10% per year on average for a US large-cap index over very long windows, with massive variation in any single year. The S&P 500 has returned ~10% nominal / ~7% real (after inflation) annualised since 1928. But annualised hides the truth — the actual experience is volatile.
| Time horizon | Historical S&P 500 outcome | What it means |
|---|---|---|
| 5 years | 1.4× to 1.7× original investment | Short-term swings dominate — index funds can return anywhere from -20% to +120% cumulative over a 5-year window. |
| 10 years | 1.7× to 3.2× original investment | Drawdowns mostly recover within 10 years. Historical 10-year nominal return range for S&P 500: ~3% worst, ~13% best annualised. |
| 20 years | 3× to 6× original investment | 20-year windows have NEVER lost money in nominal USD terms for the S&P 500 since 1928. Compounding becomes dominant. |
| 30 years | 8× to 20× original investment | At the historical 10% nominal average, $10,000 invested becomes ~$175,000. The exact multiple depends entirely on contribution timing and dividend reinvestment. |
Where to buy them in your country
The mechanics are the same globally; the specific funds and account wrappers differ.
- United States. The cheapest index funds are mutual funds from Vanguard (VTSAX), Fidelity (FZROX — 0% fee), Schwab (SWTSX), and ETFs (VTI, ITOT, SCHB). Hold them in a 401(k), Roth IRA, Traditional IRA, HSA, or taxable brokerage. The 401(k) typically has a limited menu — pick the lowest-fee S&P 500 or total-market option.
- Australia. ASX-listed ETFs from Vanguard (VAS for ASX 300, VGS for global ex-AU, VDHG diversified), Betashares (A200), and iShares (IVV, IOO). Use a low-cost brokerage like Pearler, Selfwealth by Syfe, or Stake. Inside super, your fund offers index-based investment options — pick the lowest-fee version.
- Canada. TSX-listed ETFs from Vanguard (VFV for S&P 500 in CAD, VEQT for all-equity, XEQT from iShares). Hold inside TFSA, RRSP, FHSA, or non-registered. Questrade, Wealthsimple, and Interactive Brokers all support commission-free ETF buys.
- United Kingdom. LSE-listed ETFs from Vanguard (VWRL, VUSA, VEVE), HSBC (HMWO), and iShares. Hold inside Stocks & Shares ISA or SIPP. AJ Bell, Hargreaves Lansdown, Vanguard Investor UK, and Trading 212 are common platforms.
The drawbacks — what index funds can't do
Most explainers stop at the benefits. These four limitations are the flip side of the same design, and they are worth understanding before you buy rather than during the first drawdown.
- You get the market return, and never beat it. By construction an index fund tracks its index minus a fee. That is the whole point, but it means if you are hoping to outperform, this is the wrong instrument.
- You own everything in the index. Including the companies you think are overvalued, and the ones you would rather not fund. There is no filter — that is what makes it cheap.
- Diversification is not the same as protection. A market-cap-weighted index allocates the most money to whatever is already largest, so a handful of the biggest companies can drive a large share of the S&P 500's movement. “Diversified” describes the number of holdings, not how concentrated the risk actually is.
- There is no downside cushion. Index funds fall with the market: the S&P 500 dropped 37% in 2008 and 34% in five weeks in early 2020. That matters most in the years either side of retirement, when a deep drawdown hits a portfolio you have already started drawing from — the sequence-of-returns problem.
None of these are arguments against index funds for a long horizon. They are the reason the standard advice attaches a condition: money you will not need for five to ten years.
How liquid are index funds?
Two questions get merged here, and separating them answers most of the confusion. The fund is liquid. An index ETF trades on an exchange all day and you can sell whenever the market is open, with cash settling shortly after (T+1 in the US and Canada since 2024). A mutual-fund index fund does not trade intraday — your order fills once at the end-of-day NAV, so you learn the price after the close. Either way the money reaches you in days, which is a different world from selling property.
The account is often the real constraint. Money inside a US 401(k) or IRA, Australian super, a Canadian RRSP or a UK SIPP is bound by age and withdrawal rules no matter how liquid the fund is, and pulling it out early can trigger tax or a penalty. A taxable brokerage account, a UK Stocks & Shares ISA or a Canadian TFSA has no such lock. One caveat on the fund side: it is only as liquid as what it holds, so broad large-cap index funds are the most liquid, while small-cap, emerging-market and niche sector funds can trade at wider spreads in stressed markets.
Related Richify tools
❓ Frequently Asked Questions
What is an index fund in simple terms?
An index fund is a pool of money from many investors that buys all the stocks in a specific market index — like the S&P 500 (largest 500 US companies), the FTSE 100 (largest 100 UK companies), the ASX 200 (largest 200 Australian companies), or the TSX 60 (largest 60 Canadian companies). Instead of paying a fund manager to pick winners, the fund just copies the index, holds the same stocks in the same proportions, and charges a tiny fee for doing so.
You get the average return of the index (minus the fee), which historically has beaten 90%+ of actively managed funds over 20-year periods.
How do index funds make money?
Two ways. (1) Price appreciation — the stocks inside the fund go up over time, so your share of the fund goes up too. (2) Dividends — the companies inside the fund pay dividends to shareholders, which the fund either pays out to you in cash or automatically reinvests. The S&P 500 has averaged about 10% total annual return (price + dividends) over the last 30 years, with significant variation year to year (the worst calendar year in that window was 2008 at -37%; the best was 2013 at +32%).
Long-term, the compounding is what matters.
What's the difference between an index fund and an ETF?
An index fund is the strategy — passively tracking an index. An ETF (exchange-traded fund) is one of two wrappers that strategy can come in; the other is a traditional mutual fund.
ETFs trade on a stock exchange like individual stocks (you buy/sell at intraday prices), are usually slightly more tax-efficient in taxable accounts (especially in the US), and tend to have slightly lower expense ratios. Mutual fund index funds settle once a day at the end-of-day NAV (net asset value), but offer fractional-share purchases and automatic-contribution programs that ETFs sometimes don't.
Vanguard VTSAX (mutual fund) and VTI (ETF) hold essentially the same underlying portfolio — total US market — with marginally different mechanics.
What is an expense ratio and why does it matter?
The expense ratio is the annual fee the fund charges, expressed as a percentage of your invested balance. A 0.03% expense ratio means $3 per year on a $10,000 balance.
The cheapest index funds today charge 0.03-0.10% per year (Vanguard VTI, Fidelity FZROX, iShares ITOT, Schwab SWTSX in the US; Vanguard VAS or Betashares A200 in Australia; Vanguard VFV or XEQT in Canada). Actively managed funds typically charge 0.50-1.50% per year.
Over 30 years, the difference between a 0.03% index fund and a 1% active fund can cost you 25-30% of your final balance to fees alone. This is the single biggest reason index funds beat active funds over long periods.
Are index funds safe?
Index funds are not risk-free — they own stocks, and stocks fluctuate. In 2008 the S&P 500 dropped 37%; in March 2020 it dropped 34% in five weeks.
But they are diversified — owning the entire market means no single company can ruin you. The risks are market-wide drawdowns (which historically recover within a few years) and inflation (which erodes purchasing power even when your nominal balance grows).
The standard advice — invest only money you don't need for 5-10 years, diversify globally, and don't sell during drawdowns — applies in full to index funds. They are NOT insured by the FDIC / FSCS / equivalent because they aren't bank deposits.
How much should I invest in index funds?
The orthodox answer for most working-age investors: as much of your long-term savings as you can afford after covering an emergency fund and high-interest debt. The Bogleheads three-fund portfolio (US total stock + international stock + total bond) is a common starting point.
Asset allocation depends on age, risk tolerance, and tax-advantaged-account limits (401(k), Roth IRA, HSA in the US; super in Australia; RRSP and TFSA in Canada; ISA and SIPP in the UK). Use Richify's compound interest calculator to project what regular monthly contributions to an index fund grow to over 10/20/30 years at the historical S&P 500 average return.
Which index fund should I buy?
This is personal but the most common picks: For US investors — Vanguard VTI (total US market, 0.03% ER) or VOO (S&P 500, 0.03% ER) for stocks; VXUS (total international ex-US, 0.07% ER) for diversification. For Australian investors — Vanguard VAS (ASX 300, 0.07% ER), Vanguard VGS (developed-markets ex-Australia, 0.18%), or Vanguard VDHG (all-in-one diversified, 0.27%).
For Canadian investors — Vanguard VFV (S&P 500 in CAD, 0.09%) or XEQT (all-equity ETF, 0.20%). For UK investors — Vanguard VWRL (FTSE all-world, 0.22%) or HSBC HMWO.
Richify doesn't sell or recommend specific funds — these are widely-cited examples by independent finance writers. Check the expense ratio, the index tracked, and the tax-efficiency in your account type before buying.
Are index funds liquid — how quickly can I get my money out?
The fund itself is highly liquid, but the account holding it may not be, and those are two different questions people often merge. On liquidity: an index ETF trades on an exchange throughout the day and you can sell at any point the market is open, with cash settling shortly afterwards (T+1 in the US and Canada since 2024).
A mutual-fund index fund does not trade intraday — your order executes once at the end-of-day NAV, so you know the price only after the close. Either way the money is available in days, which is far more liquid than property.
The real constraint is usually the wrapper, not the fund: money inside a US 401(k) or IRA, Australian super, a Canadian RRSP or a UK SIPP is subject to age and withdrawal rules regardless of how liquid the underlying fund is, and taking it out early can trigger tax or penalties. A taxable brokerage account, a UK Stocks & Shares ISA or a Canadian TFSA has no such lock.
One caveat on liquidity itself: a fund is only as liquid as what it holds, so broad large-cap index funds are the most liquid, while funds tracking small-cap, emerging-market or niche sector indices can see wider spreads in stressed markets.
What are the drawbacks of index funds?
Four real ones, and they are the flip side of the same design. (1) You get the market return and never beat it — by construction an index fund cannot outperform its index, so if you want a shot at above-market returns this is the wrong instrument. (2) You own the whole index, including companies you think are overvalued or object to; there is no filtering. (3) Diversification does not mean protection. A market-cap-weighted index puts the most money into whatever is already the largest, so a handful of the biggest companies can drive a large share of the S&P 500's movement — 'diversified' describes the number of holdings, not the concentration of the risk. (4) Index funds fall with the market and offer no downside cushion: the S&P 500 fell 37% in 2008 and 34% in five weeks in early 2020.
That matters most in the years just before and after retirement, when a large drawdown hits a portfolio you have started drawing from — the sequence-of-returns problem. None of these are arguments against index funds for long-horizon investors; they are the reason the standard advice pairs them with a time horizon of 5-10 years or more.
Why do index funds beat 90% of active funds over 20 years?
Three structural reasons backed by SPIVA (S&P Indices vs Active) data and Morningstar's Active/Passive Barometer. (1) Fees compound — an active fund charging 1% per year has to outperform the index by 1% per year just to break even with you, which is mathematically a high bar. (2) Survivorship bias — the active funds that underperform get shut down, so the average performance of surviving active funds looks better than reality. (3) The market is dominated by professional traders — when one beats the index, another must lose to them; collectively, active managers ARE the market (minus fees). Over 20 years, ~85-95% of active US large-cap funds underperform the S&P 500 net of fees, depending on the SPIVA report year.
Project your index-fund growth with Richify
7-day free trial on iOS and Android. Track your portfolio, set retirement goals, and get AI-powered analysis from Felix and the agent team.
Get Richify — 7-day free trial