The local media has been reporting that an "independent study" commissioned by Detroit Belle Isle Grand Prix founder Roger Penske estimates the annual IndyCar race generated $58 million in 2017 local spending.
But that's not really so, reports Tom Perkins of Metro Times:
A copy of the report obtained by Metro Times shows that its author estimates the race generates about $20 million in local income, which is the measure of an event's economic impact. But there's good reason to believe the true income level is much lower than that.
The study — funded by Penske — was put together by Sportsimpacts, a St. Louis-based consulting firm. In pushing its narrative, Penske's team chose to ignore an important sentence in the study.
“After accounting for regional income multipliers which track how much new
spending is retained within the region after it is spent, it is concluded that $20.5 million ... will be retained locally as new income for local households, businesses, and government within the greater Detroit area,” the report states. In other words, there's a $20 million benefit to metro Detroit, not $58 million.