[bjourne]

I would and have asked: Given two employees, employee A who works eight hours/day and produces X units of work and employee B who only works four hours/day but produces 2X units of work, which one would you prefer assuming both A and B are paid the same salary?

If they don't answer the question, or answers that they prefer employee A, or claims that the scenario is unrealistic because one developer can't be four times as productive as another, then I will probably not be a good company fit.