Sentence:  In this model , then , the industry is presumed to realize that they could successfully resist a change in the basic wage rate , but since such a change is the only <WSD>effective</WSD> means to raising prices they may , in circumstances to be spelled out in Part 2 , below , find it to their advantage to allow the wage rise . 
Meaning of the word marked with <WSD> tags:  exerting force or influence