Ideal taxation system must follow normal distribution:
http://www.itl.nist.gov/div898/handbook/pmc/section5/gifs/no...
where:
x - income
f(x) - taxes
For example: $5k annual income = 0% taxes $10k - 10% taxes $75k - 150k - 35% taxes $150k - $250k - 30% $250k - $1kk - 25% $100kk - 1%