The Formula for the Donovan Index determines the rate at which teams and cities win championships. Using the Dallas Cowboys, our equation would be:

Let's make our example concrete by looking at the Cowboys at their peak in 1995. Super Bowl XXX was the Cowboys' 5th title, but the titles are not equal. In 1971, the NFL had 26 teams; in 1977, 1992, and 1993, it had 28; and in 1995 it had 30. We call this discrepancy the "Riordan Factor", and it impacts how many points we award the Cowboys. Since 1995 was the Cowboys 36th season, we determine their 1995 index score as follows:

It thus follows that an average score is 1.00. In a ten-team league, a team should win once every ten years. The Cowboys were at 3.89 in 1995, meaning they were almost four times more successful than the average team at that time. Today, not having won anything in 21 years, they're at 2.50. The city of Dallas currently scores a 1.24. It's that simple.