No way to prove what you prevented. For example, preventing a texting while driving death. Via Nassim Taleb Antifragile.
Much about health is also about prevention of diseases. You never know what types of food, drink or lifestyle is “unhealthy” until *after* you’ve gotten the disease or must do an emergency surgery for some gall bladder or liver trauma.
Also with investments, you cannot prove how you *prevented* someone from going bankrupt, you can only show the profits and gains.