The change in GSP from 2019 through 2021 is in part due to the Census body count correction that occured in 2020 as well as a GSP decline as a result of COVID.

Billions of dollars (nominal); Gross State Product is a measurement of a state's output; it is the sum of value added from all industries in the state. ... GDP is the market value of goods and services produced by labor and property in the United States, regardless of nationality.

To do per capita figures, intercensus estimates of population are used and as we get along in the decade there tends to be some variation from reality. This has an impact in Census years when the actual numbers come in. In Vermont, our 2020 Census population was a very large increase from the 2019 estimate.