Harry Markowitz

Harry Markowitz received his PhD in economics from the University of Chicago, where he developed the ideas that would become his most enduring contribution to finance. His 1952 paper "Portfolio Selection" in the Journal of Finance — just 14 pages long — introduced the concept of mean-variance optimisation, arguing that investors should evaluate portfolios not by the expected return of individual securities but by the expected return and variance of the entire portfolio. The key insight was that combining assets with less-than-perfect positive correlations reduces portfolio variance without proportionally reducing expected return — the mathematical foundation of diversification. This gave rise to the concept of the efficient frontier: the set of portfolios offering the maximum expected return for each level of risk. Markowitz's framework transformed investment from an art into a science, providing the first rigorous mathematical language for the trade-off between risk and return. It became the foundation of the Capital Asset Pricing Model developed by William Sharpe, and its practical descendants include Black-Litterman, risk parity, and factor investing. Markowitz received the Nobel Prize in Economic Sciences in 1990 jointly with William Sharpe and Merton Miller. His framework is embedded in the portfolio construction process of virtually every pension fund, endowment, and institutional asset manager globally. He continued to refine his ideas throughout his career, extending portfolio theory to multi-period settings and incorporating transaction costs.