Just check if their earnings are rising (and if they are rising faster than for other workers):
Concerns about the science and engineering job market are not rooted in a classic labor market shortage. The earnings of scientists and engineers are not rising rapidly, relative to other highly educated workers. There are no massive job vacancies in academe, business, or government. If rapidly rising pay is the primary signal of a market shortage, then the United States has a shortfall of CEOs, professional athletes, entertainers, and hedge fund managers, not scientific and engineering specialists.
Then why is there a serious concern about this 'problem'? Click on that link for Richard B. Freeman's discussion of perceived problems.
Thanks to Mark Thoma for the pointer.