That was the question posed in this recent contest.
As usual, it didn’t take long for the correct answer to be posted. In this case, it came from one P. Mardel, commenter No. 3:
Both introduced low-cost interventions that had dramatic results. Both were also ostracized by the then-conventional wisdom. Ignatz Semmelweis promoted hand-washing in maternity wards, Robert S. McNamara introduced seat belts in Ford cars.
We tell the stories of Semmelweis and McNamara in greater detail in SuperFreakonomics, but it is hard to improve on P. Mardel’s rendering. Nicely done. P. Mardel wins two tickets to our Symphony Space lecture tonight.