modern portfolio theory
An investment framework developed by Harry Markowitz showing how rational investors can construct portfolios to maximize expected return for a given level of risk through diversification.
Example
“Modern portfolio theory demonstrated mathematically that combining assets with low correlations reduces risk without sacrificing expected returns.”
Memory Tip
MPT = diversification REDUCES RISK. Combining uncorrelated assets is mathematically superior to concentration.
Why It Matters
Modern portfolio theory helps individual investors understand that spreading money across different investments can reduce risk without necessarily reducing returns. This principle forms the foundation for most investment advice today, from robo-advisors to financial planning, making it essential knowledge for anyone building long-term wealth.
Common Misconception
Many people believe that diversification means simply owning many stocks or funds, but the theory is actually about selecting investments that move differently from each other. Owning 20 similar tech stocks provides far less protection than owning stocks, bonds, and other asset classes that respond differently to market changes.
In Practice
An investor with 100,000 dollars might allocate 60 percent to stock index funds and 40 percent to bonds. During a market downturn where stocks drop 20 percent, the bond portion may stay stable or gain value, reducing the overall portfolio loss to around 12 percent instead of the full 20 percent decline.
Etymology
MODERN (contemporary, Markowitz-era) PORTFOLIO (collection of assets) THEORY (framework). Markowitz's 1952 theory of optimal PORTFOLIO construction.
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