It is a question for my project. It also says ‘think about comparing the prices of things in different counties’ as a hint. Any ideas?
Bad hint. GDP per capita, even GDP per capita using purchasing power parity, is a bad measure because it only reflects the total monetary output of the economy; it says nothing about how that output was achieved, which is really what development was all about.
As an extreme example, consider Qatar. Its nominal per capita GDP is #2 or #3 in the world:
http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita
Its GDP (PPP) per capita makes it #1 or #2 in the world:
http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)_per_capita
But Qatar makes most of its money by selling oil and natural gas
https://www.cia.gov/library/publications/the-world-factbook/geos/qa.html
Its economy is not developed. For example, every developed economy has a large services sector. (For the U.S., it is 76.9% of GDP, even for China it is 40.5%)
https://www.cia.gov/library/publications/the-world-factbook/geos/ch.html
For Qatar it is only 34.1% - by this metric Qatar is less developed than China.
Qatar’s literacy is under 90% and the expected number of years in school is only 13. As developed countries go, Greece is pretty poor (per capita PPP GDP of $32,100, less than a third of Qatar’s), but even it has a literacy rate of 96% and a mean number of school years of 17.
https://www.cia.gov/library/publications/the-world-factbook/geos/gr.html
Similarly for Brunei
https://www.cia.gov/library/publications/the-world-factbook/geos/bx.html
Kuwait
https://www.cia.gov/library/publications/the-world-factbook/geos/ku.html
and other underdeveloped countries rich in resources and even money.
The traditional metrics for economic development (as opposed to wealth of the economy) used to be things like tons of steel or sulphuric acid per person. But that was in the days of the manufacturing sector.
One could argue that today it is more likely to be something like the number of personal computers per person.