The study considered data from all 50 states and Washington DC, defining "high-earning households" as ones with adjusted gross incomes of $200,000 or more. Specifically, the study looked at 

Inflow of young tax filers making $200,000 and above. This is the number of tax returns for people aged 26 up to 35 with adjusted gross incomes of at least $200,000 who moved into a state. Data comes from the IRS and for tax year 2021.

Outflow of tax filers making $200,000 and above. This is the number of tax returns for people aged 26 up to 35 with adjusted gross incomes of at least $200,000 who moved out of a state. Data comes from the IRS and for tax year 2021.