Per capita income
The 
per capita income for an area may be defined as the total personal income in an area, divided by the number of people in that area.
A ranking of the top 10 countries, according to the 1999 CIA World Factbook
-  Luxembourg $32,700
-  United States $31,500
-  Bermuda $30,000
-  Switzerland $26,400
-  Singapore $26,300
-  Hong Kong $25,100
-  Monaco $25,000
-  Norway $24,700
-  Cayman Islands $24,500
-  Belgium $23,400