Companies - which pay corporate income tax - left Detroit because of increases in personal income tax? Detroit's decline was due to suburban sprawl and the automobile-driven nature of the city's design encouraging workers who had the means to leave downtown and move out to the suburbs, gutting the tax base. This resulted in a decline in city personal income tax revenue, badly stressing city finances and further contributing to the population migration. The result was urban decay. Importantly, this had everything to do with personal income taxes, and nothing to do with business decisions; companies didn't care where an employee's taxable residency was, they simply cared that they could get to work on time.