Data: Bureau of Labor Statistics; Chart: Axios VisualsThe U.S. labor market looks to be in a precarious balance, in solid shape for the moment but vulnerable to a rapid worsening.The big picture: That's the implication of the chart above, which captures the relationship between the rate of job openings and unemployment. Based on this historical experience, if employers were to pull back on the number of job postings even slightly, it would coincide with a rapid rise in the jobless rate.It helps ...