This chart comes from an article I started a thread on a few days ago and it seems to be relative to the topic.
The graph is based around the average household income in the US. They get that average by taking the incomes of every household in America and adding them together, then taking that number and dividing it by the total number of households.
The red line on the graph is the one relative to this discussion. It shows the percentage of the average household income that's used to pay taxes. Right now that looks to be between 17% and 18%, which according to that chart, hasn't been this low since around 1970.
Since factors like the employment rate and the state of the economy effect that percentage, I decided to add some of my own additions to that graph... Take a look: