Here's a simple Hans Rosling-esque chart on population and income in the past 30 years.
How to read the chart
The background colors show the income thresholds today: Low-income in red, Medium-income in blue, and high-income in yellow. The bubbles denote countries, sized by their popoulation. The colors of the bubbles indicate what level of income they had in the start year (1987).
Once you start playing the animation through time, you'll see the movement of countries to the "income regions." This can give you a sense of which countries actually graduated from the low-income to the middle-income (there's quite a lot!); and the middle-income to the high-income (not so much).