If we were ranking ourselves, Kansas City Chiefs fans would say that we are the No. 1 fan base in the NFL. This is due to Kansas City being a smaller market yet still consistently selling out and owning one of the NFL's best home crowds.
The data says something else. It does not say that the Chiefs are the top fan base.
A study posted by Emory University attempted to rank the "best" fans based on a number of factors, including:
In terms of the nuts and bolts of what we are about to present, we use fifteen years of data on NFL team performance, ticket prices, market populations, median incomes, won-loss records and multiple other factors. We create statistical models of box office revenue, and then see which teams over- and under- perform the model's predictions.
More details on their model are here.