What is an index fund and why VTI/VOO?
Own the entire market at minimal cost.

Section 1 · What an index fund actually is

An index fund is a fund designed to match the performance of a market index, not beat it.

The S&P 500 index: the 500 largest US companies by market capitalization. An S&P 500 index fund holds all 500 stocks in proportion to their market cap. When a company grows, its weight in the fund grows. No manager picks stocks. No manager charges high fees to do so.

ETF vs mutual fund

• ETF: trades on an exchange like a stock. You buy and sell at market price during trading hours.
• Mutual fund: priced once per day at close. You buy and sell at the next day's net asset value.

For long-term investing the difference is minimal. Pick the lower-expense option from a major provider (Vanguard, Fidelity, Schwab).

Section 2 · The three-fund portfolio

Popularized by John Bogle (founder of Vanguard) and the Bogleheads community verify×DON'T TRUST, VERIFYClaim: The three-fund portfolio was popularized by John Bogle and the Bogleheads community.Verify at: Bogleheads three-fund portfolio wiki ↗The Bogleheads wiki is the canonical reference for the philosophy and implementation..

Fund 1: Total US Stock Market

• Holds every publicly traded US company. Large, mid, and small cap in proportion to market cap.
• Vanguard: VTI (0.03% expense ratio)
• Fidelity: FZROX (0.00% expense ratio)
• Schwab: SCHB (0.03% expense ratio)

Fund 2: Total International Stock Market

• Every publicly traded company outside the US. Developed and emerging markets.
• Vanguard: VXUS (0.07% expense ratio)
• Fidelity: FZILX (0.00% expense ratio)
• Schwab: SCHF (0.06% expense ratio)

Fund 3: Total Bond Market

• US investment-grade bonds, government and corporate. Lower return than stocks, lower volatility.
• Vanguard: BND (0.03% expense ratio)
• Fidelity: FXNAX (0.025% expense ratio)
• Schwab: SCHZ (0.03% expense ratio)

verify×DON'T TRUST, VERIFYClaim: Expense ratios for VTI, VXUS, BND, FZROX, FZILX, FXNAX, SCHB, SCHF, SCHZ as listed.Verify at: Vanguard fund pages ↗ · Fidelity fund research ↗ · Schwab Asset Management ↗Expense ratios change rarely but check current values before purchase.

Section 3 · Asset allocation

The stock/bond split depends on your age and risk tolerance.

US vs international allocation

One of the most debated questions in passive investing. The honest position: we do not know whether US or international will outperform going forward. Holding both eliminates the need to predict.

Common splits within the stock portion: 60-70% US, 30-40% international.

The Bitcoin holder's view

Bitcoin serves a function similar to international diversification and inflation protection. A Bitcoin holder might simplify to US stocks plus Bitcoin, reducing bond and international allocation. The full case is in Bitcoin Allocation. The honest counter: Bitcoin's volatility is not the same as bonds' stability, and it is much shorter-history than the S&P 500.

Section 4 · Why expense ratios compound

An expense ratio is the annual fee a fund charges, expressed as a percentage of your investment.

• 0.03% on $100,000: $30 per year.
• 1.00% on $100,000: $1,000 per year.

The difference compounds. $10,000 invested for 40 years at 7% gross return:

• 0.03% fund: approximately $146,600
• 1.00% fund: approximately $102,900
• Difference: approximately $43,700

Add $500 per month over 40 years at the same return:

• 0.03% fund: approximately $1.31M
• 1.00% fund: approximately $978,000
• Difference: approximately $330,000

The 1% fee is not 1% of your returns. It is 1% of your entire balance every year. Over decades the compounding cost is enormous. See Expense Ratio Impact Calculator for your specific numbers.

Section 5 · Tax-loss harvesting (taxable accounts only)

Selling an investment at a loss to realize a tax deduction, then buying a similar (but not identical) investment to maintain market exposure.

Example

1. You hold VTI (Total US Market).
2. VTI drops 20%.
3. You sell VTI, realizing a $20,000 capital loss.
4. You immediately buy SCHB (similar exposure, different fund family).
5. You have a $20,000 tax loss to offset other gains. Your market exposure is unchanged.

The wash-sale rule

You cannot buy the "same or substantially identical" security within 30 days of selling at a loss. VTI and SCHB are different enough (different fund families, different underlying indexes) to avoid the wash-sale rule verify×DON'T TRUST, VERIFYClaim: The wash-sale rule prohibits repurchasing the same or substantially identical security within 30 days of selling at a loss.Verify at: IRS Topic 409 ↗"Substantially identical" is interpreted by tax professionals; consult a CPA for edge cases..

Bitcoin is currently not subject to the wash-sale rule. You can sell at a loss and immediately repurchase. Verify whether legislation has changed this in your tax year. See Tax-Loss Harvesting for the full mechanics.

When it matters

• Only useful in taxable accounts. Not relevant in IRAs or 401(k)s.
• Most impactful during market downturns when you have other gains to offset.
• Up to $3,000 of net losses per year can offset ordinary income; the rest carries forward.

Section 6 · Factor investing: what the academic research says

In 1993, Eugene Fama and Kenneth French published a paper showing that the returns of diversified stock portfolios were not explained by market exposure alone. A three-factor model (market, size, value) explained roughly 90% of the variation in returns across 25 test portfolios, compared to about 60% for the prior single-factor capital asset pricing model verify×DON'T TRUST, VERIFYClaim: Fama and French (1993) found a three-factor model explained ~90% of return variation across diversified test portfolios.Verify at: Fama, E.F. and French, K.R. "Common Risk Factors in the Returns on Stocks and Bonds," Journal of Financial Economics 33(1) ↗The 1993 paper has nearly 15,000 academic citations and is foundational to modern asset pricing..

In 2015, Fama and French extended the model to five factors, adding profitability and investment patterns. The five-factor model is the current workhorse of empirical asset pricing verify×DON'T TRUST, VERIFYClaim: The Fama-French five-factor model adds profitability and investment to the original three factors.Verify at: Fama, E.F. and French, K.R. (2015) "A Five-Factor Asset Pricing Model," Journal of Financial Economics 116(1) ↗The 2015 paper improved explanatory power to roughly 95% across diversified portfolios..

The five factors

• Market: stocks pay more than risk-free assets in exchange for risk.
• Size (SMB, small minus big): small companies have outpaced large companies on average.
• Value (HML, high minus low book-to-market): cheap stocks (low price relative to book value) have outpaced expensive growth stocks.
• Profitability (RMW, robust minus weak): profitable companies have outpaced unprofitable ones.
• Investment (CMA, conservative minus aggressive): companies that grow assets slowly have outpaced those growing assets aggressively.

Each premium has decades of out-of-sample evidence across countries. The premiums are not constant. They go through long stretches of underperformance. From 1926 through 2020, US small-cap value stocks beat US large-cap growth stocks by more than 4 percentage points annualized over the full period, but underperformed for stretches longer than a decade.

Practical implication: a total-market index fund captures the market factor and weights stocks by market capitalization, which is the optimal portfolio under the single-factor model. Investors who want exposure to the additional factors can tilt toward small-cap value, profitability, and quality through dedicated factor ETFs. The case for tilting is the academic evidence on factor premiums; the case against is that premiums can disappear or reverse for long stretches that test most investors' patience.

Section 7 · Why most individual stocks lose

Aggregate stock market returns are positive over long periods. The returns of individual stocks are not. The distribution of single-stock returns is positively skewed: most stocks underperform, and a small number generate outsized gains that pull the average up.

JP Morgan's Agony and the Ecstasy analysis of stocks in the Russell 3000 from 1980 through 2020 found that 44% of stocks experienced a catastrophic loss (a 70% decline from peak that was never recovered). 42% had negative absolute returns. Only 10% beat the market by 500% or more cumulatively.

The implication for stock pickers: the math is against you. Picking a small number of stocks at random is much more likely to underperform the market than to beat it, because the median stock is a loser. The 2017 paper Why Indexing Works shows that when returns are positively skewed, randomly selecting a subset of securities from the index dramatically increases the chance of underperforming the index verify×DON'T TRUST, VERIFYClaim: Heaton, Polson, and Witte (2017) showed that random subset selection from a positively skewed return distribution dramatically increases the chance of underperforming the index.Verify at: Heaton, Polson, Witte. "Why Indexing Works," Applied Stochastic Models in Business and Industry 33(6) ↗The paper uses a simple model to show how positive skewness creates a structural disadvantage for concentrated portfolios..

A total-market index fund holds every stock in the market, including the small fraction that drive aggregate returns. A concentrated portfolio of a few hand-picked stocks is statistically much more likely to miss them.

Section 8 · Why the market is hard to beat (the Grossman-Stiglitz paradox)

Sanford Grossman and Joseph Stiglitz published a 1980 paper that resolved an apparent contradiction in efficient markets theory verify×DON'T TRUST, VERIFYClaim: Grossman and Stiglitz (1980) argued markets cannot be perfectly informationally efficient.Verify at: Grossman, S.J. and Stiglitz, J.E. "On the Impossibility of Informationally Efficient Markets," American Economic Review 70(3) ↗A foundational paper in financial economics. Stiglitz won the 2001 Nobel Memorial Prize in Economic Sciences..

The setup: if markets reflect all available information in prices, no one earns a return on the cost of researching stocks. But if no one researches stocks, prices cannot reflect information. The two propositions cannot both be true.

Their resolution: markets sit at a noisy equilibrium. Prices are accurate enough that the average active manager cannot beat the market net of costs, but inaccurate enough that a small number of skilled traders can earn a return on research, which keeps prices roughly accurate.

The practical implication: identifying the small set of skilled managers in advance is extremely difficult, because past performance does not reliably identify future outperformance. The 2009 Fama and French paper Luck Versus Skill in the Cross Section of Mutual Fund Returns found that only a tiny fraction of active managers have enough skill to overcome their fees, and that distinguishing them from lucky managers in advance is nearly impossible verify×DON'T TRUST, VERIFYClaim: Fama and French (2010) found that only a small fraction of active managers have skill exceeding fees, and identifying them in advance is nearly impossible.Verify at: Fama, E.F. and French, K.R. (2010) "Luck versus Skill in the Cross-Section of Mutual Fund Returns," Journal of Finance 65(5) ↗The paper uses bootstrap simulations to separate skill from luck in 30+ years of fund returns..

For most investors, the correct response to noisy market efficiency is to own the market at minimum cost rather than trying to identify the rare manager who will beat it.

Section 9 · What returns to actually expect

A common assumption is that stocks return 10% per year on average. That figure comes from the nominal annualized return of the S&P 500 from roughly 1950 to 2023, which was 11.32% nominal and 7.63% real (after inflation). Real returns matter, not nominal returns, because nominal returns do not put food on the table.

Why the post-1950 US figure is misleading

A significant portion of the post-1950 return came from rising valuations, not from earnings growth. The 2002 Fama and French paper The Equity Premium found that the realized 1951-2000 equity premium was nearly three times their estimate of the expected premium, and attributed the difference primarily to declining discount rates (rising valuations) verify×DON'T TRUST, VERIFYClaim: Fama and French (2002) found the realized 1951-2000 equity premium was nearly 3x the expected premium, primarily due to declining discount rates.Verify at: Fama, E.F. and French, K.R. (2002) "The Equity Premium," Journal of Finance 57(2) ↗The paper uses dividend and earnings models to separate expected from unexpected components of historical returns..

Rising valuations cannot be repeated indefinitely. High valuations imply lower expected future returns, not higher. From 1900 through 2023, US stocks returned 5.57% real before 1950 and 7.63% real after. Global stocks excluding the US returned 4.35% real over the same long sample.

The difference between assuming a 10% nominal return and a 7% nominal return is enormous over long horizons. Lower expected returns mean higher required savings, lower safe withdrawal rates, and longer working years to fund retirement.

Section 10 · Home country bias and international diversification

The US is roughly 60% of global stock-market capitalization. A market-cap-weighted global portfolio holds 60% US and 40% international. Most US investors hold portfolios that are 80-100% US stocks. This is called home country bias.

The case for some home country bias

• Lower fees and lower transaction costs on US-domiciled funds for US investors.
• Tax treatment is simpler: no foreign withholding tax leakage on dividends.
• Currency exposure aligns with consumption: a US investor pays for groceries in USD, so US stocks hedge local consumption better than foreign stocks.
• Foreign investors have historically faced expropriation, capital controls, and asset freezes during wars and political crises. Domestic stocks are not exposed to that specific risk.

The case against extreme home country bias

• One country is one country. Concentration in any single market exposes you to idiosyncratic political, regulatory, and economic risks.
• Past US outperformance is partly attributable to luck and rising valuations that cannot be repeated indefinitely.
• The 2024 paper Beyond the Status Quo by Anarkulova, Cederburg, and O'Doherty used 38 countries of return data from 1890 through 2023 and found that an optimal lifecycle portfolio held roughly 33% domestic and 67% international stocks verify×DON'T TRUST, VERIFYClaim: Anarkulova, Cederburg, and O'Doherty (2024) found an optimal lifecycle allocation of ~33% domestic and ~67% international stocks across 38 countries.Verify at: Anarkulova, Cederburg, O'Doherty. "Beyond the Status Quo: A Critical Assessment of Lifecycle Investment Advice" (2024) ↗The paper uses block bootstrap to simulate 1 million lifecycles from 2,600+ years of country-month return data..

A reasonable middle ground for a US investor: 60-70% US stocks, 30-40% international. This captures the diversification benefit of international stocks while preserving the cost, tax, and currency advantages of holding domestic equities.

Section 11 · Common stock-market myths

Myth: stock splits boost returns

A stock split (e.g. 2-for-1) doubles the number of shares outstanding and halves the price per share. Total market value is unchanged. A holder of 100 shares at $200 ends with 200 shares at $100. Same $20,000 of stock either way. The cash flows the company will produce, the assets it owns, and the earnings it generates are unchanged. Only the share count and per-share price are different.

Stock splits sometimes correlate with positive short-term price action. The reason is signaling: companies tend to split after a sustained price rise, which itself reflects strong fundamentals. The split is a side effect, not a cause. Studies that control for the underlying performance generally find no excess returns attributable to the split itself verify×DON'T TRUST, VERIFYClaim: Studies controlling for underlying firm performance find no excess return attributable to stock splits per se.Verify at: Ikenberry, Rankine, and Stice (1996) "What Do Stock Splits Really Signal?" Journal of Financial and Quantitative Analysis ↗The signaling literature on stock splits is extensive. Lakonishok and Lev (1987), Ikenberry et al. (1996), and subsequent studies isolate the signal effect from the split mechanic itself..

Myth: a strong economy means strong stock returns

Economic growth and stock returns are not the same thing, and historically they have been weakly related at best, occasionally negatively related verify×DON'T TRUST, VERIFYClaim: Cross-country studies find weak or negative correlation between long-run GDP growth and equity returns.Verify at: Dimson, Marsh, and Staunton, Credit Suisse Global Investment Returns Yearbook ↗Dimson-Marsh-Staunton document this across 21 countries from 1900-2012. Ritter (2005) finds the same in a separate sample.. The reason: stock prices reflect expected future cash flows discounted to today. When a country is expected to grow rapidly, that expectation is already priced into the stocks. Returns come from the gap between actual outcomes and expectations, not from the level of growth itself.

Three other reasons aggregate GDP growth does not translate cleanly to stock returns: (1) public companies are a subset of the economy and not always representative, (2) much of GDP growth is captured by labor and new firms rather than existing public-company shareholders, and (3) dilution from new share issuance reduces per-share growth even when aggregate growth is strong.

The practical implication: do not pick stocks or markets based on economic forecasts. By the time the forecast is consensus, prices reflect it.

Stock buybacks: not free, not always good, not always bad

A stock buyback is a company using cash to repurchase its own shares. The repurchased shares are retired or held in treasury. Existing shareholders end up owning a slightly larger percentage of the company. There are two common framings, both partly wrong:

• "Buybacks are free returns": not quite. The company is spending cash, which had its own economic value. The shareholders received that value as a higher ownership percentage instead of as a dividend. Same total return, different form.
• "Buybacks destroy long-term value": sometimes true, often not. A buyback at a price below fair value transfers wealth from selling shareholders to remaining shareholders. A buyback at a price above fair value destroys value for remaining shareholders. Like any capital allocation decision, the question is the price paid relative to the underlying business value.

There is also a tax angle. In a taxable account, a buyback returns capital to shareholders without triggering a taxable event for non-selling holders, while a dividend creates an immediate tax liability. This is one reason many companies have shifted from dividends to buybacks since the 1980s.

For an index investor, buybacks happen across the portfolio constantly and net out as just another way the underlying companies allocate capital. There is no special "buyback strategy" that systematically beats the market.

Volatility is not the same as risk

Volatility (the size of price swings over short windows) is the financial industry's default proxy for risk because it is easy to measure. For long-term investors with real-world spending needs, volatility is a poor proxy. The risk that matters is permanent loss of purchasing power: not having enough money when you need to spend it.

Cash and short-term Treasuries have very low volatility. They also have a strong historical record of losing real (inflation-adjusted) purchasing power over multi-decade horizons. Stocks have high short-term volatility but have historically outpaced inflation over long horizons most of the time. For a 30-year-old saving for retirement, "low-volatility" cash is almost certainly riskier than "high-volatility" stocks. The cash position is more likely to fall short.

The takeaway: use volatility as a behavioral constraint (you cannot hold an asset you will sell at the bottom), not as a risk metric. The actual risk metric is the probability of failing to meet your goals.

Bond duration: how bond prices move when rates change

When interest rates rise, existing bond prices fall. When rates fall, existing bond prices rise. This is always true. Mechanically: you hold a bond paying 3%; rates rise to 5%; new bonds pay 5%; nobody wants your 3% bond at full price; its price falls until its yield matches the new market rate.

Duration measures how sensitive a bond's price is to interest-rate changes, expressed in years. A bond with duration 7 falls roughly 7% in price when rates rise 1%. Longer-maturity bonds have longer duration. A 30-year Treasury has duration around 18 to 20 years; a 2-year Treasury has duration around 1.9 years.

The 2022 stress test

Vanguard's BND total bond market ETF has duration of approximately 6 years. When rates rose roughly 4 percentage points across 2022, BND fell approximately 13% on a total-return basis - the worst calendar year in its history and one of the worst for any major bond index since data started verify×DON'T TRUST, VERIFYClaim: Vanguard's BND fell approximately 13% in 2022, its worst calendar year, driven by rapidly rising interest rates.Verify at: Vanguard BND fund page (annual returns) ↗ · FRED 10-year Treasury rate ↗Bloomberg US Aggregate (the BND benchmark) had its worst calendar year on record in 2022 according to standard fixed-income databases.. This surprised many investors who assumed bond funds were a safe haven.

Bonds are safe from credit risk (a Treasury will not default in the conventional sense). They are not safe from duration risk. The two are different.

Convexity

Duration is a linear approximation. Convexity captures the curvature of the price-to-rate relationship. Most standard bonds have positive convexity: they gain slightly more from a rate decrease than they lose from an equal rate increase, which is good for the holder. Mortgage-backed securities often have negative convexity because homeowners refinance when rates fall, prepaying the high-yield mortgages and removing the upside.

What this changes for your money

• Short-term bond fund (1 to 3 year duration, e.g. VGSH, BSV): limited rate sensitivity, lower yield, protects principal. Right for money you need within 3 to 5 years.
• Intermediate bond fund (5 to 7 year duration, e.g. BND, AGG): moderate rate sensitivity. Right for the bond portion of a long-term portfolio that can absorb temporary losses.
• Long-term bond fund (15+ year duration, e.g. TLT, EDV): high rate sensitivity. Only appropriate for very long horizons or specific tactical bets, not as a generic "safe" sleeve.
• In a rising-rate environment, shorter duration beats longer duration. In a falling-rate environment, the order reverses.
• The lesson from 2022: BND is the default bond fund in many target-date and three-fund portfolios. Many holders did not know its duration and were shocked by the loss. Knowing the duration of any bond fund before adding it is the practical takeaway.