It's the idea that basically, the increment to wages that a worker requires to leave him indifferent between performing two tasks -- one which is more unpleasant than the other -- that's what you call a "compensating differential."
Ideja je u tome da povećanje plaće koji radnik zahtjeva kako bi ostao indiferentan u obavljanju dvaju zadataka -- od kojih je jedan neugodniji od drugog -- to se zove kompenzacijska razlika.