From a full-page ad in the New York Times signed by more than 200 economists, including three Nobel laureates:
More government spending by Hoover and Roosevelt did not pull the United States economy out of the Great Depression in the 1930s. More government spending did not solve Japan’s “lost decade” in the 1990s. As such, it is a triumph of hope over experience to believe that more government spending will help the U.S. today.
If I observe that exercise didn’t by itself solve the weight problems of persons A and B, should I infer that it won’t help C?