Money & WorkMental model
The only free lunch in investing.
Diversification means spreading money across many assets that don't fall at the same time. If a company goes bankrupt, you lose everything with one stock but 0.1% with 1,000 stocks. The expected return stays the same; only the volatility drops. Spread across industries, countries and asset classes, because ten car stocks aren't real diversification.
Useful: For every investment, ask: what happens to the rest if this one fails?
Source: en.wikipedia.org