There are six kinds of unemployment stats the US tracks (below). Nothing sounds specific to underemployment by skills specifically (maybe u-6?). That would probably come from other metrics, like quintile income distributions shifting downwards?
You didn't ask, but just in case (from an internet search):
U-1: Long-term unemployed
* Definition: People unemployed 15 weeks or longer, as a percentage of the civilian labor force.
* Purpose: Measures persistent unemployment.
U-2: Job losers and temporary workers
* Definition: People who lost jobs or completed temporary jobs, as a percentage of the labor force.
* Purpose: Captures recent layoffs and temp contract ends.
U-3: Official unemployment rate (headline rate)
* Definition: Total unemployed as a percentage of the civilian labor force.
* Purpose: This is the standard "unemployment rate" reported in news and economic discussions.
* Definition: U-3 plus discouraged workers (those who want a job but stopped looking because they believe no jobs are available).
* Purpose: Adds a layer of marginal attachment to the labor force.
U-5: Unemployed + All marginally attached workers
* Definition: U-4 plus all others marginally attached to the labor force, not just discouraged workers.
* Marginally attached workers: People not currently working or looking for work but who want a job and have looked in the past 12 months (but not the past 4 weeks).
U-6: Broadest measure
* Definition: U-5 plus part-time workers who want full-time jobs (i.e., involuntary part-time workers).
* Purpose: The most comprehensive measure of labor underutilization, including: Discouraged workers, Marginally attached workers, and Underemployed part-timers
You didn't ask, but just in case (from an internet search):
U-1: Long-term unemployed
* Definition: People unemployed 15 weeks or longer, as a percentage of the civilian labor force.
* Purpose: Measures persistent unemployment.
U-2: Job losers and temporary workers
* Definition: People who lost jobs or completed temporary jobs, as a percentage of the labor force.
* Purpose: Captures recent layoffs and temp contract ends.
U-3: Official unemployment rate (headline rate)
* Definition: Total unemployed as a percentage of the civilian labor force.
* Purpose: This is the standard "unemployment rate" reported in news and economic discussions.
* Limitations: Doesn’t count discouraged workers or part-time workers wanting full-time jobs.
U-4: Unemployed + Discouraged workers
* Definition: U-3 plus discouraged workers (those who want a job but stopped looking because they believe no jobs are available).
* Purpose: Adds a layer of marginal attachment to the labor force.
U-5: Unemployed + All marginally attached workers
* Definition: U-4 plus all others marginally attached to the labor force, not just discouraged workers.
* Marginally attached workers: People not currently working or looking for work but who want a job and have looked in the past 12 months (but not the past 4 weeks).
U-6: Broadest measure
* Definition: U-5 plus part-time workers who want full-time jobs (i.e., involuntary part-time workers).
* Purpose: The most comprehensive measure of labor underutilization, including: Discouraged workers, Marginally attached workers, and Underemployed part-timers