The Return on Management ratio
ROM can be expressed as the following equation: ROM = Productive energy released divided by management time and attention invested.
This ratio—which is more of a metaphor than an exact calculation—provides a framework for evaluating your strategic focus on daily tasks. Is your energy invested in activities that best contribute to your organization’s productivity and overall performance? If not, you are likely not spending your time on the “right” opportunities and challenges.
In the case of developing employees, the ROM ratio suggests that managers spend the most time working with the people that contribute the most and add the most value to the organization. This group would consist of both star performers and solid contributors. Based on such an assessment, the third group, your low-potential, low-performing employees (or C players), would merit the least management time and energy because they benefit the organization the least.
Excellent post on specific ways to help different kinds of people improve, with links to even more specifics for "A," "B," and "C" players.