Média Variância Estimativa (MVE) is a fundamental concept in finance and statistics used to assess the risk and return profile of investment portfolios. Developed by Harry Markowitz in the 1950s, MVE provides a structured way to select assets that maximize expected returns for a given level of risk.
A ideia central por trás da MVE é analisar a mean (average retorno esperado) e variance (measure of risk) of different assets. By combining these two metrics, investors can create a diversified portfolio that balances potential gains with acceptable levels of risk.
In practical terms, MVE involves calculating the expected return of individual assets and their correlations with one another. This allows investors to understand how assets might perform together, as some assets may offset risks associated with others. The goal is to construct an ‘efficient frontier’ of optimal portfolios that provide the highest expected return for a given level of risk.
Mathematically, the expected return of a portfolio is calculated as the weighted sum of the expected returns of its individual assets, while the variance is derived from the weights of the assets, their individual variances, and their covariances. This complex interplay forms the basis of Modern Portfolio Theory (MPT).
Embora a MVE seja amplamente utilizada, ela possui limitações, especialmente na sua dependência de dados históricos para prever retornos e riscos futuros, o que nem sempre é válido. Além disso, assume que os investidores são racionais e que os mercados são eficientes, o que pode levar a discrepâncias na aplicação no mundo real.