Non-linear monotonic decreasing transformation approach: This data transformation approach is suggested byGolany and Roll (1989). It converts an ‘undesirable’ output into a ‘normal’ or ‘desirable’ output by a monotonically decreasing function f of the form: f(uik)=1/uik, where uik is the ith element of the vector u of undesirable outputs of DMU k. In such a manner, performance would be inversely related to the undesirable output. Lovell et al(1995) compare the macroeconomic performance of 19 OECD countries using the same approach: The reciprocals of undesirable outputs (carbon and nitrogen emissions) are treated as normal outputs.