Why spreading money across different holdings reduces risk — and why it doesn't eliminate it.
If you own one stock and it drops 50%, your portfolio drops 50%. If you own twenty unrelated stocks and one drops 50%, the damage to your overall portfolio is far smaller — diversification means no single company's bad outcome can sink the whole portfolio.
Diversification reduces company-specific risk (a bad product launch, an accounting scandal, one company's bankruptcy) very effectively. It does much less for systemic risk — a broad recession or market-wide selloff still drags most stocks down together, diversified or not.
Ten stocks in the same sector or theme aren't meaningfully diversified — if that sector has a bad year, all ten move together. Real diversification comes from holding companies that don't move for the same reasons, which usually means spreading across different sectors and business models, not just adding more tickers.
Too few holdings concentrates risk in a handful of bad outcomes; too many makes a portfolio hard to actually follow and tends to just converge toward the market average anyway. There's a practical middle ground, not a single right number.
Sector vs. industry — how this site classifies companies Value, growth, and dividend stocks — what's the difference?
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