If Vietnam's GDP last year was $1 billion, and this year it's $1.082b, that's an 8.2% growth.

Lets assume that GDP is entirely from selling widgets.

Last year they sold 108 billion widgets and received $1b dollars, 108 widgets for a dollar. They spend that $1b on 1 million units of oil.

This year they produce the same 108 billion widgets, but this time they will only say 100 widgets for a dollar, so they get 108b - 8% growth.

They then spend that $108b on 1 million units of oil (as oil is more expensive)

Has the economic output really grown 8%?

Or is it that they are still making 108 billion identical widgets as last year, so no change in output, just charging more, but the dollars they get will buy less oil?

Or are GDP figures adjusted for inflation?