Stock market basics · updated October 21, 2026
What is diversification and why does it matter
Diversification means spreading your money across many companies, sectors, countries and types of assets, so one bad investment cannot wreck your whole portfolio. It is the only way to cut risk without giving up return.
How it works
The less your investments move together, the steadier your portfolio. Ten banks from the same country are not diversification, because they fall together. Real diversification mixes different sectors (technology, healthcare, energy), different countries and different assets (stocks, bonds, cash). The simplest way is an ETF on a broad index, which holds hundreds of companies.
Worked example
You own 10 stocks, with 10% of your money in each. One of them falls 50%.
If all your money had been in that one stock, you would have lost half.
Worth knowing
Diversification does not protect you from a fall of the whole market: in big crises almost every stock drops at once. It protects you from the problems of a single company or a single sector.
When diversification can fool you
Too many similar things: five ETFs on US tech are really one investment. Too much: beyond a few dozen stocks, each new one adds less and less protection.
Related terms
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Questions about diversification
How many stocks do you need to be diversified?
Classic studies show that 20-30 stocks from different sectors remove most of the risk tied to any one company. An ETF on a broad index does that in one go.
Does diversification lower returns?
It lowers the chance of a huge win from a single stock, but also of a huge loss. Over the long run, the average return stays close to the market's.
These explanations are for information only. They are not a recommendation to buy or sell.
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