Which of the following most logically completes the argument?
Yorco and Zortech are two corporations that employ large numbers of full-time workers who are paid by the hour. Publicly available records indicate that Yorco employs roughly the same number of such hourly wage workers as Zortech does but spends a far higher total sum per year on wages for such workers. Therefore, hourly wages must be higher, on average, at Yorco than at Zortech, since _____.

【选项】the proportion of all company employees who are hourly wage workers is significantly greater at Yorco than it is at Zortech