Good question. When taxes are down to 3% flat (across the board for fairness sake)the GDP is going to increase so significantly that 3% should cover it comfortably ! :)
You are kidding, right? If 2005 GDP was $12.5 trillion, you realize that 500 billion is ALREADY 4% of that - not including your "internal" police spending - how much do you think GDP is going to increase in year 1, for instance?