问道伤脑筋的逻辑题

Although the ratio of physicians to total population is about the same in the United States and Canada, the United States has 33 percent more surgeons per capita. Clearly, this is the reason people in the United States undergo 40 percent more operations per capita than do Canadians.

The explanation given above rests on an assumption that

(Patients in the United States do not have a greater need for surgery than do patients in Canada).

Thank you.

My understanding is that if there are more operations in one area per capita, there can be one of two reasons behind it: 1)more people are ill and so more people need surgery. 2)not many people need surgery, but the doctors think they need it in order to make more money.

Now the argument says that "this (33 percent more surgeons per capita) is the reason people in the United States undergo 40 percent more operations per capita than do Canadians."

That is reason #2 above, so reason #1 should be eliminated.

That is, the assumption should be "Patients in the United States do not have a greater need for surgery than do patients in Canada."