what is marginal value at risk var 
marginal var is a calculation of the additional risk that a new investment position will add to a portfolio or a firm it is simply an estimate of the change in the total amount of risk not the precise amount of risk that a position is adding to or subtracting from the whole portfolio that more precise measurement is known as incremental var the bottom linevalue at risk var is a well known commonly used risk assessment technique the var calculation is a probability based estimate of the minimum loss in dollar terms expected over a period the data produced is used by investors to strategically make investment decisions var is often criticized for offering a false sense of security as var does not report the maximum potential loss one of its limitations is that the statistically most likely outcome isn t always the actual outcome 