That is just one of the numerous things people say because they've heard so many people say it. The fact is, there isn't and never was any economic basis on which to make the blanket statement that lowering taxes will increase government revenue. Otherwise the tax rate would be 0.5% and the government would be swimming in money. But it's not 0.5% because they wouldn't be. All things being equal the Laffer curve is an accurate representation of the actual impact of tax rates on tax collections. Simply put, the effect of a lower or higher tax rate depends on where you are on the Laffer curve. Hence, you could easily lower rates and get more revenue or raise rates and get more revenue. Going from a 5% income tax to a 10% income tax would raise more money than going from 10% to 5%. Likewise, going from 45% to 55% would likely raise less money.

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I wasn't born with enough middle fingers.