Good summary. However what the study suggests is that a Fair Tax would be superior to a flat tax. Flat taxes still fall on investment, savings and work. Supply side is not an economic theory, it is an empirical observation about the impact of taxes and some taxes have a greater negative effect than others. Economics in contrast is a general theory that helps us make sense of these empirical observations which in turn reinforce neo-classical, positive and Austrian school economics and further debunk Keynesian economics.