The circles indicate industries, sized by their average number of employees over time. From there, the chart is doing two things — tracking jobs and earnings from 2006 to 2017 (the up and down movement of the circles shows the change in number of jobs; left to right is the change in earnings), and projecting forward from 2014 to 2024 (signified by the intensity of the colors of the circles).
Data: Bureau of Labor Statistics; Graphic: Chris Canipe / Axios
Go deeper: A snapshot of the jobs malaise