The replacement metric for GDP? Is not part of the problem that we have a single metric for just about anything?

If it is the material well being of a population you want, then I suggest national wealth/capita (and better to look at median then average). National wealth being the sum of stuff within the borders. This was as I understand it the dominant metric before GDP, and was probably abandoned because GDP is so available: just check the total tax bases from the stats collected by the tax office.

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