How an Earnings Tax Harms Cities Like Saint Louis and Kansas City
"The economics is quite straightforward. By adopting an earnings tax, a city gives businesses and residents an incentive to locate production outside the city. People go where they will obtain the highest after-tax return on their labor or investments."
From the Four Page Policy Briefing linked at the above article:
"An earnings tax is systematically associated with lower city percapita income relative to the surrounding suburbs."