This ratio is quite straight-forward. How much revenue does a company need to take in to produce how much net earnings? While this ratio will differ between business models, it is a good comparison to show how one company sits compared to its competitor.
N= per dollars of revenue Revenue Efficiency = (Net earnings / Revenue) x N
Charting this ratio historically will also give you an idea of future prospects. Ultimately an investor would like this number to be as high as possible.