Adjusting for PPP allows us to make a more accurate "apples to apples" comparison of GDP per capita among countries around the world by adjusting for the differences in prices in each country. For example, the UK's unadjusted GDP per capita was $45,729 in 2014, but because prices there are higher on average than in the US (for food, clothing, energy, transportation, etc.), the PPP adjustment lowers per capita GDP in the UK to below $40,000. On the hand, consumer prices in South Korea are generally lower than in the US, so that increases its GDP per capita from below $28,000 on an unadjusted basis to above $34,000 on a PPP basis.

As the chart demonstrates, most European countries (including Germany, Sweden, Denmark and Belgium) if they joined the US, would rank among the poorest one-third of US states on a per-capita GDP basis, and the UK, France, Japan and New Zealand would all rank among America's very poorest states, below No. 47 West Virginia, and not too far above No. 50 Mississippi. Countries like Italy, S. Korea, Spain, Portugal and Greece would each rank below Mississippi as the poorest states in the country.