what is ex post 
ex post is another word for actual returns and is latin for after the fact the use of historical returns has customarily been the most well known approach to forecast the probability of incurring a loss on investment on any given day ex post is the opposite of ex ante which means before the event sydney saporito investopediaunderstanding ex postex post information is attained by companies to forecast future earnings ex post information is utilized in studies such as value at risk var a probability study that approximates the maximum amount of loss that an investment portfolio may incur on any day var is defined for a specified investment portfolio probability and time horizon ex post yield differs from ex ante yield because it represents actual values essentially what investors earn rather than estimated values investors base their decisions on expected returns vs actual returns which is an important aspect of an investment s risk analysis ex post is the current market price minus the price that the investor paid it shows the performance of an asset however it excludes projections and probabilities calculating ex postex post is calculated using the beginning and ending asset values for a specific period any growth or decline in the asset value plus any earned income produced by the asset during the period analysts use ex post data on investment price fluctuations earnings and other metrics to predict expected returns it is measured against the expected return to confirm the accuracy of risk assessment methods ex post is best used for periods less than a year and measures the yield earned for an investment year to date for example for a march 31 quarterly report the actual return measures how much an investor s portfolio has increased in percentage from jan 1 to march 31 if the number is 5 then the portfolio gained 5 since jan 1 ex post analysisex post performance attribution analysis or benchmark analysis gauges the performance of an investment portfolio based on the return of the portfolio and its correlation with numerous factors or benchmarks ex post analysis is the traditional approach of performance analysis for long only funds ex post performance analysis typically centers on regression analysis an analyst executes a regression of the portfolio s yields vs the returns of the market index to determine how much of a portfolio s profit and loss might be the result of market exposure the regression provides the portfolio s beta to the market index and the amount of alpha the fund was gaining or losing in relation to the market index ex post forecastingthe formula for calculating ex post is ending value beginning value beginning value the beginning value is the market value when an asset was purchased the ending value is the current market value of an asset ex post is a forecast prepared at a certain time that uses data available after that time the forecasts are created when future observations are identified during the forecasting period it is used to observe known data to assess the forecasting model 