Asset classes explained: equities, bonds, commodities, and why diversification across them matters

Asset classes are the fundamental categories through which financial markets are organised. Equities, fixed income, commodities, currencies, cryptocurrencies, and alternatives each represent a distinct type of economic exposure—different return drivers, different risk characteristics, and different behaviour under the same market conditions. Understanding what asset classes are, and why allocating across them reduces portfolio risk, is the starting point for any serious multi-asset investment approach.

What an asset class is

An asset class groups assets that share the same underlying economic characteristics. They respond to similar drivers, tend to move together over time, and behave differently from assets in other classes. Equities are driven by corporate earnings and growth expectations. Fixed income responds to interest rates and credit conditions. Commodities reflect physical supply and demand for goods. These are not administrative groupings: assets within the same class behave similarly because they represent the same type of economic claim.

The distinction between an asset class and an asset type is central to how pfolio classifies assets, and it matters in practice. An asset class describes the exposure—what economic risk is being taken on. An asset type describes the instrument—the vehicle through which that exposure is held. An ETF can give equity exposure, commodity exposure, or fixed income exposure depending on what it tracks: the instrument type is the same; the asset class differs entirely. For a full treatment of this distinction, see Asset types explained.

Why diversification across asset classes matters

The case for holding assets across multiple classes rests on correlation. When two assets move in the same direction at the same time—highly correlated—combining them reduces concentration but provides limited risk reduction. When two assets have low or negative correlation, combining them reduces portfolio volatility without proportionally reducing expected return. This is the mechanism through which diversification generates value beyond simply holding more assets.

Diversification within a single asset class offers only partial protection. In severe equity market downturns, equities across geographies and sectors tend to become highly correlated with each other—the within-equity diversification benefit shrinks precisely when it is needed most. Assets from genuinely different classes, with different return drivers, maintain their diversifying properties more reliably across market conditions. For a detailed treatment of how correlation works in practice, see Correlation in portfolio management.

The six standard asset classes

Equity represents ownership in companies. Returns come from price appreciation and, for dividend-paying stocks, income distributions. Equities have historically delivered strong long-run returns but with significant volatility and the possibility of severe drawdowns. They are the primary growth engine in most multi-asset portfolios, and the asset class most self-directed investors encounter first. Equity investing explained

Fixed income covers bonds and bond-like instruments—loans to governments and corporations that pay periodic interest and return principal at maturity. Returns come from yield and from price movements as interest rates change. Fixed income has historically provided portfolio stability relative to equities, though duration risk—the sensitivity of bond prices to rising interest rates—is a material structural vulnerability. Fixed income investing explained

Commodity exposure covers physical goods: precious metals, energy products, and agricultural goods. Commodity prices respond to physical supply-and-demand dynamics rather than corporate earnings, which gives commodities genuine diversifying properties relative to financial assets. Returns come entirely from price movements and roll yield—there is no yield or cash flow—which limits their long-run return potential relative to equities or bonds. Commodity investing explained

Currency as an asset class refers to holding foreign exchange exposure as a return driver in its own right, not merely as a transactional necessity. The primary return sources are carry—borrowing in a lower-yielding currency and investing in a higher-yielding one—trend, and relative monetary policy. FX exposure can add diversification to a multi-asset portfolio, though it is characterised by lower long-run expected returns and volatility that is difficult to forecast. Currency investing explained

Cryptocurrency—primarily Bitcoin and Ethereum as the most widely held examples—are digital assets with decentralised issuance and extreme volatility. Their return history is short relative to other asset classes, which limits the reliability of long-run statistical analysis. Correlations with equities have increased as institutional ownership has grown, reducing the diversification benefit that early proponents cited. Any allocation should reflect the asset class's volatility and the concentration of custody and regulatory risk. Cryptocurrency investing explained

Alternatives is a catch-all category for assets and strategies that do not fit neatly into any of the five standard classes. In pfolio, the primary examples are volatility products and instruments linked to the VIX index, which measures implied equity market volatility. Volatility products tend to rise in value during equity market stress, providing a form of portfolio protection, but they carry negative cost of carry in normal market conditions and produce episodic rather than consistent returns. They are complex instruments and not suited to all portfolios. VIX and volatility investing explained

Portfolio—pfolio's seventh asset class

In addition to the six standard asset classes, pfolio uses a seventh classification: Portfolio. This designation applies to assets that are themselves multi-asset portfolios—a model portfolio, fund-of-funds structure, or multi-strategy vehicle tracked as a single investable instrument in the platform. This is a pfolio-specific classification with no standard industry equivalent. It enables users to include benchmark portfolios and model strategies in the same analytical framework as individual assets, and to compare their performance and risk characteristics directly. For a full explanation, see Portfolio instruments.

Asset classes in pfolio

Every asset in pfolio carries an asset_class tag—one of the seven classifications described above. These tags are visible on the Assets page and drive the filtering and selection logic in the Portfolios section: asset class filters define the investable universe before the algorithm selects and weights individual assets. Asset class performance and risk metrics across holdings are available in pfolio Insights.

Related articles

• Asset types explained: how ETFs, stocks, futures, and currencies differ as investment instruments
• Correlation in portfolio management: why diversification depends on it
• Sharpe ratio explained: measuring risk-adjusted portfolio returns
• Portfolio variance: understanding return dispersion and investment risk