To complicate matters, there is not neccessarily a correlation between the compression reading and any loss of horsepower. You would need to know where the leakage was occuring. As 411 mentioned, TCM has loads of data that prove leakage past the dynamic seal, (rings), during a compression check does not represent what is occuring under engine operation, in fact they significantly lowered the compression test limits for leakage past the dynamic seal.
Leakage past the valves during the comp test is a better indicator of what will result in a loss of horsepower during operation.