By Gabriele Denaro · Published 20 September 2026 · Updated 6 October 2026
Diversifying means owning several things whose prices do not all rise and fall at the same time, so a bad year for one does not damage everything at once. It does not guarantee a positive return, and nothing does. What it does is narrow how bad the worst realistic outcome can be.
Take two investments that each swing wildly. In year one A gains 30% and B loses 10%. In year two A loses 10% and B gains 30%. Either one alone ends up 17% higher after two years. Held half and half and rebalanced each year, the portfolio gains 10% in both years and ends 21% higher. The example is deliberately extreme, because the two assets are built to move in opposite directions. Real assets are rarely that cooperative, but the principle holds: partly offsetting swings make the ride smoother and can raise the compounded result.
In severe crises, assets that normally move differently can fall together for a while. Diversification lowers the chance that everything goes wrong at once. It does not remove market risk, and it cannot protect you from buying things that are expensive or poorly understood.
You can spread across asset classes such as stocks, bonds and cash, across regions and sectors, and across time. There is also diversification outside the portfolio: if your salary and your savings both depend on the same employer or industry, a single event can hit both. Holding a lot of your employer's stock makes that overlap worse.
Ten funds that hold the same companies are not diversified, they are repeated. Past a point, extra holdings add cost and complexity without adding protection. This guide is a structural principle, not a recommendation of any fund, sector or allocation: what suits you depends on your goals, your timeline and how much loss you can tolerate.
General educational information, not personal financial, tax or legal advice. It may be incomplete or out of date. Terms of use.