I would use size of the circle to represent that country's population.

Once that was done you'd have more large circles on the left on top of each other, so then I'd stretch it vertically to make it easier to read.

Another way to reduce the clutter on the left would be using a log (or sort-of-log) scale for income. Because it's possible that a small increase in income in a poor country corresponds to a significant decrease in road death rate, and this would something worth noting.