Plain-English investing notes, one idea at a time — every number checked against a primary source.

Portfolio & RiskGlossary

Diversification

Diversification means spreading money among different investments so one loss hurts less. Plain-English definition, a worked example and its limits.

Also called: diversifying, spreading risk, not putting all your eggs in one basket

By The Token Thesis Desk2 min read4 cited sources

A heap of many differently coloured glass marbles
“JM marbles 01” by Joe Mabel — CC BY-SA 3.0 (edited: cropped, recolored)

Quick answer

Diversification is spreading your money among different investments — across asset types such as stocks and bonds, and within each type — so that a loss in one holding has a smaller effect on your whole portfolio.

What does diversification mean?#

Investor.gov sums diversification up as "Don't put all your eggs in one basket": spreading your money among various investments in the hope that if one loses money, the others will make up for those losses[1]. The SEC's beginners' guide adds that a diversified portfolio should be diversified at two levels — between asset categories, such as stocks and bonds, and within each category[2].

A portfolio is everything you hold, counted together. Diversification is a property of that whole, not of any single investment in it.

What does diversification look like with numbers?#

Worked example

One holding falls 50% in a $10,000 portfolio

If all $10,000 is in one stock and it falls by half, you lose $5,000. If the $10,000 is split equally across 20 holdings and one of them falls by half, you lose $250.00 — 2.5% of the portfolio — assuming the others hold their value.

Portfolio splitLoss if one holding falls 50%Share of portfolio lost
1 holding (100%)$5,000.0050.0%
20 holdings (5% each)$250.002.5%

Figures computed in code from the stated inputs; rounded to the nearest cent or tenth.

What can diversification not do?#

FINRA notes that diversifying doesn't ensure a profit or guarantee against loss[3]. When most markets fall at the same time, a diversified portfolio falls too. Diversification shrinks the damage any single holding can do; it does not decide how much overall risk you take. That is the job of asset allocation.

In the U.S., federal pension law requires many retirement-plan benefit statements to warn that holding more than 20 percent of a portfolio in the security of one entity, such as employer stock, may not be adequately diversified[4]. That is a disclosure rule, not a universal limit, and rules differ by country.

Where will you see this term?#

You will see it in fund descriptions, retirement-plan statements and nearly every beginner's guide. Broad funds are a common route: the SEC notes that a total stock market index fund can own stock in thousands of companies[2] — see index funds explained. For the full explanation with tables, read diversification explained; to see how a diversified mix is kept on target over time, see rebalancing.

Sources

Numbers in brackets in the text point here. Grade A = primary source (regulator, statistics agency, law or official document).

  1. 1
    Diversification (glossary)U.S. SEC — Investor.gov (n.d.) · Grade A
  2. 2
    Beginners' Guide to Asset Allocation, Diversification, and RebalancingU.S. Securities and Exchange Commission (SEC.gov) (n.d.) · Grade A
  3. 3
    Know Your Risk ToleranceFINRA (2024) · Grade A
  4. 4
    29 U.S. Code § 1025 — Reporting of participant's benefit rights (ERISA §105)U.S. Code via Cornell Legal Information Institute (current) · Grade A

How we checked this note

Every number, date and rule above links to its source. This note cites 4 sources, 4 of them primary (Grade A). Worked examples were calculated in code, and a second editor compared each figure with its source before publishing. Spotted an error? Tell us — corrections are listed on the note. Read our editorial policy.