Index Fund or Single Stock?

Not two answers to the same question: one buys the market, the other buys a company, and the risks come from different places.

The question "which stock should I buy?" usually skips the question before it: do you want to pick one company, or carry the whole market? They are not the small and large versions of the same job. Where the return comes from, where the risk comes from and what can mislead you are different in each.

The Average Stock Is Not Average

The stock market's long-run return is not spread evenly across stocks. The distribution is skewed: a large number of ordinary or poor outcomes is balanced by a very small number of enormous winners.

The Numbers Behind the Picking Problem

~4%

Share of Stocks That Produced All of the US Market's Net Wealth Creation, 1926-2016

>50%

Share of Stocks Over the Same Period That Returned Less Than One-month Treasury Bills Over Their Lifetime

~90%

Share of US Large-cap Active Funds Trailing the S&P 500 Over Fifteen-year Windows

The first two lines come from the same study, and read together they say this: a single randomly chosen stock has less than an even chance of matching the market average. An index holds those few big winners by definition; it never has to know which ones they will be. The third line shows that professionals find the job hard too.

A Single Stock Carries Two Risks

When you buy one stock you carry both market risk and company-specific risk. The second can be diversified almost to zero with diversification; the first cannot.

The consequence matters: the market does not pay extra for a risk you could have diversified away. Holding a single stock means taking more risk, but the expected return does not rise automatically in exchange. For it to rise, the pick has to actually be right.

Side by Side

Topic	Index Fund	Single Stock
The Bet	On the market as a whole	On that company beating the market
Cost	Annual expense ratio, usually low	No expense ratio, but research time
Bad Scenario	Falling with the market	A company-specific collapse, down to zero
Monitoring Load	Low	Earnings every quarter, news, guidance
How You Get It Wrong	Timing	Timing and selection

When a Single Stock Makes Sense

Buying a single stock is a legitimate choice; you just need to know you are making a claim. That claim is usually defensible under three conditions:

You have a view on the company, and it differs from what the market has priced in. "Good company" is not a view; good companies are already priced expensively. More: P/E and the Valuation Ratios
You have the time to follow it. Reading earnings, tracking guidance changes and noticing when the thesis breaks all take continuity.
The position size is limited. One company collapsing doesn't take your portfolio somewhere you can't carry. More: Risk Management

Some investors think in two layers for this reason: most of the portfolio in a broad index, a small part in companies they hold a view on. That is not a recommendation, just a frame that accepts the two tools do different jobs.

Where You'll See It on This Site

On the Compare screen you can draw a stock on the same scale as SPY or QQQ: what the pick added or took away relative to the index reads off a single chart. ETF pages show a fund fact box instead of company metrics.

Your Place in the Guide

Article 5 of 49 in the Guide

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