Dear Lurker-Jerk,
Suppose I produce $300,000 a year in goods and services and the tax code breaks out--hypothetically--something like this:
$0 to $20,000 - 0%
$20,001 to $40,000 - 10%
$40,001 to $80,000 - 25%
$80,001 to $250,000 - 45%
$250,001 and above - 70% (we all know you would prefer 90% but bare with me)
Now, since I make $300,000 I'd be taxed at 70% which means I lose $210,000 reducing my netincome to only $90,000.
If I shot for $250,000 in annual income--FIRST, I just lowered my productivity by one-sixth and anytime productivity drops by 16% the economy contracts by an equal amount--but my tax burden becomes $112,500 leaving me with $137,500 net income. In other words, it's worth more to me personally to produce less for other people.
That means people deprived of my knowledge, skills and products. It also probably means I hire fewer employees, patronize fewer vendors, spending less money when I procure my own life's needs and wants...oh and by the way I'm also paying $97,500 less in taxes.
But that's OK because progressive taxation incentivizes non-production. In fact, once the tax rate creeps north of 50% you're telling me I'm working more for other people than I am myself and my family. Well, guess what: I'm a free bunny and the 13th amendment says you cannot take my labor for free or compel me to work.
Now suppose that 45% was applied flatly to my $300,000 income. That's $135,000 in taxes leaving $165,000 net to me.
$165,000 net is quite a bit more than $90,000 so I might stay on the job. The economy won't shrink and while $135,000 is less than $210,000--which you won't get because I won't work to pay it--it is more than $112,500 by nearly a fifth.
So would you rather grow revenues by 1/5 or shrink the economy by 1/6?