Results are not enough

Of course, results are a very important part of a manager's evaluation.  But that's not the end of the story...

Consider the manager of a great team of engineers. One can expect that the team will deliver good results. And this may be the case even if the manager is not so great... Conversely, let's consider the manager of a bad team: it may be the case that whatever the manager will do, the team will not deliver. In the long run, a great manager will manage to improve the results he gets from the team, but it may take quite some time. Evaluation of the managers only from the team's results is thus not enough, and may even be completely counter-productive...

So what's a good manager to do?

Of course, a manager must make plans. But that's not enough: as Tom Foster puts it, managers should build robust plans that take external factors not under their control into account. And they should be judged on the fact that they not only planned for success, but made it more likely to happen. Luck, or the lack of it, should not play a role. Kids learning chess often setup traps, only to discover that their opponent did you fall into it. They plan for the best, instead of planning for the worst. Explicitly supposing that things can go wrong is a good way to not depend on random external factors, and improve the likelihood of getting good results.

Getting results is not the mark of a good manager.  Consistently getting results is.