The Wall Street Journal shows the following chart which pits two metrics against each other:
The primary metric is the change in median yearly salary between the two periods of time. We presume it's primary because of its presence in the chart title, and the blue bars being more readable than the green bubbles. The secondary metric is the median yearly salary in the later period.
That, I believe, was the intended design. When I saw this chart, my eyes went to the numbers inside the green bubbles. Perhaps it's because I didn't read the chart title first, and the horizontal axis wasn't labelled so it wasn't obvious what the blue bars coded.
It's simply impossible to know what values should be in each bubble, or to perceive the relative sizes of those bubbles.
Reversing the order of the blue bars also helps:
The original order is one of the more annoying features in most visualization packages. Because internally, the categories are numbered 1, 2, 3, ..., and because the convention is to have values run higher as they run up the vertical axis, these packages would place the top-ranked item at the bottom of the chart.
Most people read top to bottom, which means that they read the least important item first, and the most important item last!
In most visualization packages, it takes only 1 click or 1 action to reverse the order of the items. Please do it!
For change over time, I like using a Bumps chart, otherwise called a slope graph: