Most of us understand the concept of marginal tax rates just fine. We're arguing about the optimal shape of the curve. Everyone (with a few exceptions) seems to prefer that the curve should trend up sharply just past their own income level.
At least half, and I would say as a hand-waving number, maybe as much as 75% of the comments I see in any online comment thread to any news-y-ish thing demonstrate a complete failure to understand marginal tax rates.
Closer to home: my kids don't understand it. My wife doesn't understand it. Most of my in-laws don't understand it.
