In finance they use the terms Alpha and Beta which would be very applicable here. I'm not an expert, but my understanding is that Alpha is the improvement in excess of average market improvement. So if your investments are returning 8%, knowing that the S&P500 went up 7% over the same time period is critical information especially compared to the same 8% when the S&P500 went down 2% over that time period. I think beta is just that average of market returns.

Perhaps we could develop Alpha and Beta for violence as a better tool to understand what works and what doesn't.