The success of our economy is predicated on the basis that our most productive individuals and businesses will continue to progress and be innovative. When tax rates are abnormally high, then more time and energy is spent on tax avoidance(a more appropriate term than tax evasion), and less time and energy to the conduct of their business.
There are entire industries based on helping wealthy individuals and prosperous business limit their exposure to income, sales, and estate taxes. IMHO, this is an inherently inefficient use of capital, but that's the way it goes. I'm a CPA who earns his livelihood from this industry, but I do not fear my prospects outside of this industry.
There is plenty of evidence out there that shows the inverse relationship between the level of tax rates, and revenues received by government. When tax rates are perceived to be 'fair', less avoidance and evasion take place. Conversely, when taxes are not perceived as 'fair', more effort is placed on reducing one's burden to a 'fair' level, consistent with ever-changing tax laws. I have seen this firsthand over the past 10 years.
i still don't see this holding in every day life. people will work harder if it means they get more money. you talk as though there were some kind of salary cap.