The issue with GDP-replacements is that GDP is a good proxy for many things, not just one. GDP / capita is a proxy for well being. GDP is a proxy for how credit

The issue with GDP-replacements is that GDP is a good proxy for many things, not just one. GDP / capita is a proxy for well being. GDP is a proxy for how credit worthy a country is. It's good proxy for how well a country could wage war if they switched to war economy. It's proxy for how much slack there is in the system that could be used to deal with bad times.