When I sent in my federal tax last year, I took the tax actually paid and divided by the gross pay and my tax rate was about 3%. This is all due to exemptions and credits. The 2 main things that reduced my tax was Housing deductions and deductions for charitable donations. Plus I did not make that much money since my wife lost her job at BOA and had to take a part-time job that paid less.
If you tax the sale of stock you slow down investment. Investors can invest at foreign exchanges and avoid the tax. What we want is foreign investors to invest in America. You obviously do not understand the concept of investing or economics. I do however see how we could have a service fee for every stock purchase. I see some advantage in paying a tax at the time of the sale of stock in certain cases. However, a few things are going on that you should be aware of. The first is that many people invest in stock by using margin which is borrowing money to invest in stock. This type of investing may dry up if you had to pay the tax up front. Then there is shorting stock and options which would may also be affected by having to pay a tax. Then there is the fact that some people make a huge profit on some stocks and you would be losing the 15% on the capital gains. As an example if 2 years ago you purchased Apple stock you could be losing half of the country's capital gains on just that stock.
So if you have a flat tax, it will hurt the poor an awful lot if they have to pay a 20% tax on food. The other problem is when the economy slows down there will be an immediate slowdown on the revenue. However, with Income Tax, it takes at least 6 months to a year for the federal govt to feel the pain of an economic slow-down. I think we need a hybrid system. The thing about the rate of a flat tax on sales is that there are no loop holes so you dont need that high a rate. Also keep in mind that if you are collecting sales tax you have to chase after all the businesses that dont send in their tax money. Sales tax is easier for businesses to cheat on and it has a higher maintenance fee for the IRS. With income tax the IRS and the revenue department gets their money right away from payroll deductions. The Feds would lose this free gift.
Everything has its pros and cons.