Gain-to-Pain Ratio

Two strategies can have the same Sharpe ratio yet feel completely different to trade: one loses money in small, frequent dribbles, the other in rare but painful lumps. The gain-to-pain ratio is built to capture that "pain" directly, using monthly returns rather than the volatility of daily returns that the Sharpe ratio relies on.

The formula sums every monthly return, then divides by the absolute value of the sum of only the negative months:

$$GPR = \frac{\sum_t R_t}{\left|\sum_{t:\,R_t<0} R_t\right|} .$$

The numerator is just the strategy's total return over the period. The denominator adds up every losing month's magnitude — a single $−8% month contributes far more to the denominator than eight separate $−1% months, even though both sum to the same loss. That is the point: unlike a metric that merely counts down months, gain-to-pain penalizes concentrated pain more than spread-out pain of the same total size.

As a worked example, suppose a strategy returns $+3\%, +2\%, -4\%, +1\%, -2\%, +3\%$ over six months. The sum of all months is $3+2-4+1-2+3 = 3\%$. The sum of losing months is $-4 - 2 = -6\%$, so its absolute value is $6\%$. The gain-to-pain ratio is $3/6 = 0.5$ — meaning the strategy's cumulative gain is only half the size of its cumulative pain, a weak result even though it has more winning months than losing ones. A ratio above roughly 1.5–2 is generally considered a respectable track record; a ratio near or below 1 signals that the losing months are doing serious damage relative to what's being earned.