Apparently this belief is far more common than I thought. I expected it to be closer to the percentage of Americans who think the Earth is flat (10%)[0]. Evidently 50% of Americans[1] believe you pay your highest marginal rate on all of your income. I'm blown away, and genuinely humbled. I don't understand how someone can get a Fannie Mae/Freddie Mac home loan, raise children, have a long and successful career and not understand tax brackets -- I clearly am incredibly out of touch with how some people live their lives, and I have a lot to learn about other people.
0: https://carsey.unh.edu/publication/conspiracy-vs-science-sur...
1: https://www.aei.org/economics/survey-confirms-that-many-amer...