I don't know that "the 'happiness index' might be a better way to measure the wealth and growth of a nation" but GDP should not be the primary way we measure the wealth and growth of a nation. GDP actually measure neither of those nor does the happiness index. GDP measure output. Happiness index measure outcomes. To measure wealth, you would need a measure like "net worth." Add up the value of everything "American." Probably best done by sector and asset type. Government, Private, Personal, Natural. Equity, Real Estate, Commodity, Property. Growth could be measured by change in "net worth."
Measuring is good, we should measure outcomes, wealth, production and growth. We just need to better understand what we are measuring and why it matters.
TEK