For a thumbnail sketch of the national retail sales tax, aka Fair Tax, visit http://www.fairtaxvolunteer.org/smart/sketch.html
I don't know what percentage we need for the NST. I think 23% sounds high. But, by eliminating SS and totally privatizing it, we could probably get down to a more reasonable 10%, especially if we started cutting unconstitutional spending like the Dept. of Education, HUD, HHS etc.