The metaphorical difference between a thermometer, which gives you a figure but doesn’t tell you what to do about it, and a thermostat, which gives you a figure and then adjusts the heating or cooling appropriately, applies to benchmark figures. It’s a thermometer to know that most law departments in the United States have three lawyers per paralegal. That factoid gives little guidance.
It’s a thermostat if the data shows for every 20 percent increase in the ratio of lawyers to paralegals, total legal expenses as a percentage of revenue drops 10 percent. It that finding were true – and I suspect some kind of correlation like that but lack sufficient data to confirm or reject it – you would have a clear direction to follow, at least to some point.