So if looking at contemporaneous economic conditions is not a reliable way to judge presidents, how should they be graded?
Similarly, a better way to judge presidents is by the policies they pursue, not the outcomes over which they preside. This task is harder than merely looking at unemployment, inflation and the growth of gross domestic product. It requires having a view about what policies are best at fostering prosperity and acknowledging that the experts are often divided on that question.
IOW, if not the proximate data, then what? Well, how well do you reward your friends and punish your enemies? Policy changes.