IRS SOI for 2015. https://www.irs.gov/statistics/soi-tax-stats-integrated-business-data
 New York Department of Tax & Finance, Tax Facts, at: https://www.tax.ny.gov/data/stats/tax-facts.htm#expanded-content-menu3
 This is called single sales factor apportionment. Corporations doing business in the U.S. must “apportion” their profits among the different states where they do business. E.g., if a corporation makes $1 million in profit doing business in New Jersey and New York, each state cannot tax the fully $1 million. Instead, each state chooses some formula for determining how much profit that state can fairly tax. New York uses a formula based solely on where corporations have sales. In this example, if 50 percent of the corporation’s sales were in New York, New York would be able to tax 50 percent of the $1 million of profit, or $500,000.
 Cooper, M. et al (2016). https://eml.berkeley.edu/~yagan/BusinessOwnersTaxes.pdf
 C. Pulliam and R. Reeves, “The SALT tax deduction is a handout to the rich.” (Sept. 4, 2020)