Ex-Post Risk

What Does Ex-Post Risk Mean?
A type of risk measurement technique that uses historic returns to predict the riskiness of a certain investment in the future. This type of risk measure is the equivalent of the statistical variance of an asset's returns relative to its mean.

Investopedia explains Ex-Post Risk
Using historic returns as a measure of future risk has been a traditional method used by investors to determine the riskiness of a given asset. Ex-post risk is often used in value at risk analysis - a tool used to give investors a best estimate of the maximum amount of loss that they could expect to incur on any given trading day.