There is such a thing as underemployment, but I don't think it means what the gp and you are claiming. Actually I think that like unemployment, there are 2 forms of it...
1. voluntary - a person is capable of doing a job, that job is available and fits into that person's life, but (s)he chooses to work at a less demanding job not utilizing his/her skills. I don't see this as a problem, personal choice is OK.
2. involuntary - this is a case where a person or workforce has capacity to produce more, get higher wages, or otherwise be "better" employed, but market inefficencies[1] prevent the best employment. Again, this may not be a problem for the individuals - they may not be bothered by this, but it is a valuable measure for opportunity. If a company can employ these people for $fewer than the going rate, but $more than they are making and gain profit, they should, because it helps overall market efficiency - it helps lower the cost of employees overall, and helps raise the wages of the people who provide value. Everyone wins. Just like finding new sources of any raw material in demand, or using previously "too expensive" sources because the market price has shifted.
For a real example: company A had a systems office in my town employing some pretty good graybeards. A decided that they didn't want/need to be in that business anymore, and closed the office. For the large part, the graybeards were happy in town, and chose to stay and not work at as well paying jobs, for reasons outside of salary. The thing is - systems graybeards are in demand and expensive (usually). For a while they were underemployed, not making the money they should. But company B heard of this, and realized that they could pay cost-of-living adjusted salaries that saved them a lot of money on a pool of systems people with a proven track record. They opened an office hiring most of the underemployed graybeards and everything was in balance again.
Of course that example is almost the text-book ideal case of how efficiencies, indicators, and such should play out. There are harder cases of this. Finding ways to take advantage of the underemployed metric is more difficult.
Anyway -- that is the long way around of saying: underemployment may not be a good or even valid measure at a personal level, but at an aggregate level it is a good measure of where efficiency can be sought. Disbelieving it speaks more of personal/political biases than of a market understanding - probably because it is term associated often with jobs programs and other things many dislike.
[1] Like algorithms, just because a perfect theoretical algorithm has an efficiency of $X, a given implementation my only be able to achieve $Y efficiency (where $X > $Y).
1. voluntary - a person is capable of doing a job, that job is available and fits into that person's life, but (s)he chooses to work at a less demanding job not utilizing his/her skills. I don't see this as a problem, personal choice is OK.
2. involuntary - this is a case where a person or workforce has capacity to produce more, get higher wages, or otherwise be "better" employed, but market inefficencies[1] prevent the best employment. Again, this may not be a problem for the individuals - they may not be bothered by this, but it is a valuable measure for opportunity. If a company can employ these people for $fewer than the going rate, but $more than they are making and gain profit, they should, because it helps overall market efficiency - it helps lower the cost of employees overall, and helps raise the wages of the people who provide value. Everyone wins. Just like finding new sources of any raw material in demand, or using previously "too expensive" sources because the market price has shifted.
For a real example: company A had a systems office in my town employing some pretty good graybeards. A decided that they didn't want/need to be in that business anymore, and closed the office. For the large part, the graybeards were happy in town, and chose to stay and not work at as well paying jobs, for reasons outside of salary. The thing is - systems graybeards are in demand and expensive (usually). For a while they were underemployed, not making the money they should. But company B heard of this, and realized that they could pay cost-of-living adjusted salaries that saved them a lot of money on a pool of systems people with a proven track record. They opened an office hiring most of the underemployed graybeards and everything was in balance again.
Of course that example is almost the text-book ideal case of how efficiencies, indicators, and such should play out. There are harder cases of this. Finding ways to take advantage of the underemployed metric is more difficult.
Anyway -- that is the long way around of saying: underemployment may not be a good or even valid measure at a personal level, but at an aggregate level it is a good measure of where efficiency can be sought. Disbelieving it speaks more of personal/political biases than of a market understanding - probably because it is term associated often with jobs programs and other things many dislike.
[1] Like algorithms, just because a perfect theoretical algorithm has an efficiency of $X, a given implementation my only be able to achieve $Y efficiency (where $X > $Y).