My favorite graph is service level versus profitability. In this graph, we vary service level by adding staff, and track the resulting profitability. For most revenue producing centers, you should see a shape like the graph below.
This is a textbook, marginal profit curve. What we produce is a change in profitability by agent, meaning, if I hire one more person, how much will they sell, and what will they cost? If your goal was a 60% service level, you would be leaving revenue on the table. If your goal was 90%, you would be paying too much in agent costs relative to the revenue being produced. If you wanted to run the center as if it were a business, you would run a service level between 75% and 85%, in order to maximize profits.
There is a lot that goes into these graphs (and thank goodness I have CenterBridge to produce this one), but the concept is pretty straightforward. If the marginal value per call changes, these graphs shift substantially. I’ve got a few stories about the use of these in the real world, and I’ll try and post these soon.