Earlier quoted context omitted.
No one uses PPP for measuring growth, GDP PPP can increase whilst your economy contracts. PPP isn’t a good measure for population’s wealth or quality of life especially for developed economies either. The economy of the US is still twice that of the EU and its global purchasing power has also pretty much doubled.
" GDP PPP can increase whilst your economy contracts. " Still, if PPP GDP increases, with all else being equal (eg. stable population) it would imply the standard of living is increasing. That is why PPP GDP captures a more accurate measure of the real world. Said another way, what truly matters isn't "GDP growth", but changes in purchasing power/quality of life.
With some important caveats:
1. Balance of trade. The goods and services in the poorer nation are worth less, comparatively. Any trade with the richer nation will lead to a wider balance of trade deficit. This causes all kinds of structural economic and budget problems in the long term.
2. Foreign purchasing power. Customers have to substitute goods and services away from the richer nation to poorer nations. If one’s preferred television, for example, is produced in the richer nation, these will become more expensive, and will force consumers to purchase other options. This is especially acute in cases where a nation has a de facto monopoly on certain industries.
In reality, both nominal and PPP GDP figures are important to monitor for different reasons.