If tax rates were 0%, the government would take in $0.
If tax rates were 100%, the government would take in $0 (likely that nobody would work for nothing)
Obviously, the rates between 0 and 100 have the government taking in some money.
There is a particular point where that revenue is maximized.
Increasing tax rates beyond that point actually DECREASES tax revenues, as it starts to approach that $0 for 100%.
Nobody quite knows yet where that maximization point is. (It looks like 50% on the curve below, but it is obviously just for a visual aid.) Many people believe that we are already above that maximization tax rate, and that the liberal Dems care far more about control and destroying America's economy than in maximizing tax revenues.
(NOTE: The presumption that revenue maximization should even be a goal for Congress is sadly almost universal, both within the halls of Congress and within the electorate.)
