Volatility Risk Premium in 30 Lines of Python (And the 5 Mistakes That Wreck It)

The volatility risk premium (VRP) is the gap between what the options market prices in and what the underlying actually delivers. The formula fits in one line. The interesting part is in the inputs, the unit conversions, and a handful of mistakes that produce a plausible-looking but wrong number. This post walks through the math, a worked SPY example, a self-contained Python implementation in 30 lines, and the five pitfalls I see in almost every homemade implementation. TL;DR VRP = sigma_IV - si