Why Diversify?
No single asset class outperforms in every environment. In 2022, both stocks and bonds lost value. In 2020, tech and gold surged while energy collapsed. Diversification smooths the impact of these cycles.
Mathematically, diversification reduces total portfolio risk (standard deviation) below the weighted sum of individual asset risks — provided the assets are not perfectly correlated.
Dimensions of Diversification
Asset class diversification: Stocks + bonds + gold + cash. Stocks and bonds historically show negative correlation — when one falls, the other often rises.
Sector diversification: Technology, energy, healthcare, financials, consumer staples — different sectors thrive under different economic conditions.
Geographic diversification: Domestic + international + emerging markets. This reduces country-specific risk (currency, inflation, politics).
Time diversification (DCA): Investing fixed amounts at regular intervals averages out entry timing risk across market cycles.
The Danger of Over-Diversification
Holding too many positions complicates management, raises transaction costs, and dilutes outperformance. Research shows 15–20 low-correlation stocks eliminate most unsystematic risk; more positions add minimal additional protection.