Backward Propagation for Finance People
In finance, the process of retrospectively evaluating the efficacy of investment decisions is referred to as attribution. It's used to ask, "How'd we do?" and offer a granular, objective answer. Using the risk/reward framework, widely accepted risk factors are used to explain a position's performance. As a cartoon example, let's say you own a share of IBM. For equities, we'll perform attribution using Beta , roughly speaking a measure of correlation to the underlying market. If IBM has a Beta of 0.75 and the SnP5000 moved by 2% then Beta predicts that IBM would move by 0.02 * 0.75 = 1.5%. If instead we observed a measure of 1.7% then we may say that 1.7 - 1.5 = 20bps (basis point = 1/100 of 1%) is due to expert skill aka " alpha ." Alpha is often used as a remuneration metric for professional portfolio managers. There's actually a whole lot more to attribution but hopefully this example communicates the general intuition. Interesting...