Modern Portfolio Theory (MPT), developed by Harry Markowitz in 1952, remains one of the most practical frameworks for building client portfolios. At its core, MPT shows that diversification can reduce risk without sacrificing expected returns.
The efficient frontier is the set of portfolios that offer the highest expected return for each level of risk. Any portfolio below the frontier is suboptimal — you could either get more return for the same risk, or less risk for the same return.
In practice, advisors map a client's risk tolerance (1-5 scale) to a point on the efficient frontier, then recommend an asset allocation. A conservative client might hold 50% bonds and 20% US bonds, while an aggressive client might be 40% US large cap and 20% small cap.
The Sharpe ratio measures risk-adjusted return: (portfolio return - risk-free rate) / portfolio volatility. Higher is better. A Sharpe ratio above 1.0 is generally considered good.
While MPT has limitations (it assumes normal distributions and static correlations), it provides a disciplined, evidence-based framework that's far superior to gut-feel allocation. Combined with Monte Carlo simulation, it gives advisors powerful tools for client conversations.