Egidio's Gym has been in operation for seven years, and offers regular weekly weight training and aerobic classes, as well as occasional programs in dance and martial arts. The gym has seen a surge of new members in the past twelve months, despite keeping the same membership fee over the past three years. Of the 450 current members, more than 250 have joined in the past year. Clearly, the membership of Egidio's Gym has risen a significant amount because of its superior facilities.
Which of the following is an assumption on which the argument depends?