For each of the cases below, identify whether the observed wage differential is likely to be an equilibrium or a temporary differential, and explain why.
a. Pilots in one non-unionized airline earn 20 percent more than pilots in a second non-unionized airline.
b. Construction workers employed near Alberta's oil sands earn 30 percent more than similar workers in Manitoba.
c. Dental surgeons earn far more than dental hygienists.
d. Pilots in a non-unionized airline earn more than flight attendants in the same airline.