Most of the information is not public, there are a number of HBS cases with relevant data but they are all behind paywalls. If you do the math, it's clear that ebitda margin improvement, top line growth, and multiple expansion have a much larger impact on returns than debt paydown. Here are some highly quick and dirty numbers (initial equity value is negative bc it's plugged straight into IRR()): https://imgur.com/lGCs5aR