For five countries of your choice, collect the GDP per capita from unstats.un.org (any year and countries you like where all the data is available).
1. Collect the PPP (purchasing power parity) adjusted GDP per capita.
2. Use the Big Mac Index (just make an internet search for this) to adjust your nominal incomes.
3. PPP and Big Mac Index are essentially price indices. Define what a price index is. How do the GDP per capita change after accounting for price indices? Why is it important to use price index adjustments?