In the weeks leading up to the 2013 NFL draft, FiveThirtyEight published No Team Can Beat the Draft. In essence, it shows that there is no evidence that certain teams are better at drafting than others.
This means we can perform the same test at the GM level as well — and, once again, there’s virtually no relationship8 between how well a GM drafts, relative to average, from one year to the next.
The -20 to 20 scale is a measure of a players Approximate Value relative to the average Approximate Value of players selected in their draft slot.