Diversification means spreading investments across different asset classes, sectors, and geographic markets to reduce risk. The underlying logic is simple: if one investment falls in value, the others need not follow. A well-diversified portfolio typically delivers lower volatility without necessarily sacrificing return — making diversification one of the rare true "free lunches" in investing.

Diversification — why you should not put all eggs in one basket

Nobel laureate Harry Markowitz laid the mathematical foundation for Modern Portfolio Theory (MPT) in 1952, demonstrating that a combination of assets with low mutual correlation can deliver better risk-adjusted returns than any of them individually. That insight remains as valid today as it was then.

In practice, diversification is about avoiding a situation where your entire capital depends on a single outcome — one company, one industry, one country, or one asset class. The pandemic of 2020, the rate shock of 2022, and the banking collapses of 2023 are all examples of events that hit undiversified portfolios hard.

Diversification across asset classes

The first step is distributing capital across fundamentally different types of assets:

• Equities (stocks) — high expected return, high volatility. Best on long time horizons.
• Bonds — lower return, lower volatility. Often act as a buffer when stocks fall.
• Commodities — gold, silver, oil, copper. Inflation protection, low correlation with equities. See inflation hedging strategies.
• Real estate — direct property or REITs. Rental income and long-term value appreciation.
• Cash / short-term instruments — liquidity buffer and a source of dry powder for redeployment.

Diversification within an equity portfolio

Sector diversification

Stocks within the same sector tend to move together. A portfolio of only technology stocks (many of which fell 60–80% in 2021–2022) carries high sector-concentration risk. Spreading across defensive sectors (healthcare, consumer staples) and cyclicals (industrials, commodities, technology) creates a more balanced risk profile.

Geographic diversification

Investing only in your home country concentrates exposure in a single economy with its own specific risks. A globally diversified portfolio — for example via MSCI World or FTSE All-World index funds — spreads risk across the US, Europe, Japan, and emerging markets, smoothing out country-specific shocks.

Market-cap diversification

Large-cap and small-cap stocks do not always move in sync. Small caps have historically delivered higher returns but with greater volatility. A blend of both categories smooths the curve over time.

Correlation — the heart of diversification

Diversification only works if assets do not move in exactly the same direction at the same time — this is measured by correlation, on a scale from -1 (always move in opposite directions) to +1 (always move in the same direction).

Key historical correlations to understand:

• Gold / equities: low to negative during crises — gold often rises when stocks fall
• Gold / USD: often negative — a weaker dollar tends to push gold prices higher (gold is priced in USD)
• Copper / equities: positive — copper tracks economic activity
• Bonds / equities: historically negative, but the correlation rose sharply in 2022 (inflation + rate hikes)

Correlations are not constant — they shift with market regimes. During stress (2008, 2020), correlations spiked dramatically ("all correlations go to one in a crisis"). Real diversification therefore requires more than just mixing assets — it requires regular re-evaluation of the portfolio's actual correlation structure.

Rebalancing — maintaining diversification over time

Over time, a portfolio's composition drifts as assets rise and fall at different rates. If equities have rallied strongly and now represent 80% of a portfolio where the target was 60%, it is time to rebalance — selling some equities and buying more of the underrepresented assets.

Rebalancing typically happens one to four times per year, or when any asset class deviates more than 5–10 percentage points from its target weight. It is a disciplined way of "buying low and selling high" mechanically.

Commodities in a diversified portfolio

Gold and silver add diversification value primarily because of their historically low correlation with equities. An allocation of 5–15% to precious metals typically smooths portfolio volatility without drastically reducing expected returns. See live prices at guldpris.nu and silver.nu.

Copper and oil add a more cyclical commodity exposure and suit a commodity sleeve within a multi-asset portfolio. See kopparpris.se and olja.nu for live prices.

Frequently asked questions about diversification

How many stocks do I need to be diversified?

Research (Evans & Archer, 1968; Campbell et al., 2001) shows that idiosyncratic (company-specific) risk falls sharply with as few as 20–30 stocks spread across sectors. But individual stock-picking requires research — for most retail investors, a broad index fund is more practical and likely better diversified.

Can you be over-diversified?

Yes. Holding 200 individual stocks provides scarcely better diversification than 30 well-chosen sector representatives, yet requires far more management. Over-diversification can also dilute the impact of your best ideas. This is sometimes called "di-worsification" — diversification past the point of diminishing returns.

Are index funds a good diversification strategy?

Yes, for most investors. A global index fund (e.g., based on FTSE All-World or MSCI World) gives exposure to thousands of companies across dozens of countries at low cost. Add a bond fund and optionally a commodity ETF to broaden asset-class diversification.

How do I diversify against currency risk?

Foreign assets carry currency risk — if your home currency strengthens against the US dollar, the value of your USD-denominated holdings falls when translated back. You can hedge via currency-hedged fund share classes or directly via forward contracts. Alternatively, you can accept currency exposure as an additional diversification dimension. Follow EUR/USD at eurokurs.se and USD rates at dollar.nu.