In place of the name of the US State it puts a country whose dollar value of Gross DOMESTIC Product (GDP) is equal/similar to the dollar value of output of that State.
For instance, Australia's GDP is roughly the same of that of Texas's GSP. Brazil similar to California, so on and so forth.
|Source: Carpe Diem at AEI|
Here is the accompanying data in Excel form that show the numbers used for each State.