Diversification

Diversification is the practice of holding many different investments — across securities, sectors, asset classes, and countries — so that no single negative event can damage more than a small slice of your wealth. Harry Markowitz, who won a Nobel Prize for formalising this idea in 1952, called diversification "the only free lunch in finance" because it reduces risk without reducing expected return, provided the underlying assets do not move perfectly in sync.

The math works through correlation. If you hold ten stocks whose prices all move together (correlation of +1), you have the concentration of one stock. If those same ten stocks have low or negative correlations, the portfolio's volatility can fall by 30–50% versus any single holding while the average return stays the same. A typical diversified portfolio for an Indian retail investor: 30 stocks via a Nifty/Sensex index fund, international equity via an S&P 500 fund, 20–30% in PPF/debt mutual funds, a 5–10% gold allocation through SGB or ETF, and an emergency cash buffer.

Diversification helps against idiosyncratic risk (one company failing) but not against systemic risk (a global recession). It also has diminishing returns — past ~25–30 well-chosen holdings, adding more barely moves the needle.

A single global index ETF delivers instant diversification across thousands of companies and dozens of countries at an expense ratio of 0.03–0.20% — a starting point our ETF and index-fund guides explore in detail.