The Western economic literature almost universally uses the median when discussing income and wealth comparisons.
I see a lot of data expressed in GDP per capita to compare the wealth of different nations. http://www.gapminder.org/ for example uses it. The CIA Worldbook does so as well.
If the economics literature really does things different this seems to be a neat way that the CIA is actually using to push it's policy agenda.
If you have nearly data over the median income of countries all over the world over the last 100 years I would be interested in the data set.
I see a lot of data expressed in GDP per capita
GDP per capita is the aggregated Gross Domestic Product of the entire country divided by its population. It says nothing about income or wealth distribution within this country. It is also NOT the mean of personal income in that country.
GDP per capita basically tells you how much does a country produce, normalized for its population.
a neat way that the CIA is actually using to push it's policy agenda
...If you have nearly data over the median income of countries all over the world over the last 100 year
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.