I. McKinsey's interactive graph on cities
McKinsey Quarterly : Cities the next frontier for global growth (2011)
Below is my favorite graph of the hundreds you can generate yourself at this McKinsey site. It shows which cities will have the most middle class consumers (households with income greater than $20,000 per year) in the year 2025. The height of the bar represents the number of middle class households. Only the top cities (by number of middle class households) are shown. I counted 23 bars.
This graph sends a clear message to business: if you want to sell lots of product in 2025, then you need to be entering emerging markets now. By 2025, only 3 of the top 23 cities (ranked by number of prospective middle class customers) will be in the U.S..
II. Gapminder's interactive graphs on health and wealth
If this doesn't load, go to http://www.gapminder.org/ and then click on tab for Gapminder World
Below is a screenshot of one of Gapminder's interactive graphs for 1950. There was a clear distinction between groups of countries. By 2009, things look very different - only Sub-Saharan Africa and Afghanistan fall in the Developing Countries square. This explains the rise of alternative labels - like low income countries (LIC).
Click on the following link to see the graph for yourself: Gapminder "developing country" graph . If you explore the site, you will find many other graphical demonstrations of the relationships between countries' health and wealth over time.