Can someone please help me in finding out the accurate answer from the following question. Significant influences on the union non-union wage differentials comprise the: (1) Proportion of the industry which is unionized and the frequency of strikes. (2) Frequency of strikes, inflation, and the collective bargaining policies. (3) Collective bargaining policies and the stage of business cycle. (4) Proportion of industry which is unionized and the stage of business cycle.