I sympathize with the idea in this post, but I don't agree. For the system to be simple enough that more than a tiny fraction of our math-challenged population would understand their marginal rates and related figures, you would need a drastically simpler system, e.g. one with a single rate (or a very small number of rates) and no deductions or exemptions. Even just the difference between and average and a marginal rate is more than most people are going to understand. So while I like the idea of a simpler system, I think it's impossible to imagine that we'll ever have a system as simple as would be needed for the objectives you lay out. If the point is for people to understand what their marginal rate is, wouldn't it be better to just encourage tax preparer programs to make this an output of their calculations?