The chart was assembled by the research team at HowMuch using a bunch of data collected from the Organization for Economic Co-operation and Development (OECD). Specifically, they considered how large each bubble should be by looking at average household wealth for each country. If you're curious what exactly "household wealth" actually means, it's essentially a measure of one's assets minus liabilities, taking into account things like savings, securities, stocks, and loans (it doesn't take into account real estate, though). Then they shaded each bubble a distinct color based on the average disposable income for each household in that country, or the amount of income left after taxes and charges that people can spend on whatever they want.
Unsurprisingly, the United States earned the top spot when it came to household income, while Sweden and Japan came in the number two and number three positions. As for which country has the lowest average household wealth, Turkey came in last of the 36 countries that were considered, while Mexico had the second lowest, and Slovakia had the third.
Here's how the OECD ranked the top 10 highest, by both average household wealth and disposable income.