You are underpaid, but I would not say underemployed. The benefit society gains from a PhD is high, mainly because of the training students get from doing a PhD

You are underpaid, but I would not say underemployed. The benefit society gains from a PhD is high, mainly because of the training students get from doing a PhD. But there is an over-supply of students who want to do PhDs as opposed to the budget for science, so the pay is very low.