And the Bush tax cuts reduced revenues to the government. So, from a Laffer curve perspective, we can see what side of it they reside upon. Here's the CBO link showing their effect on revenues:
http://www.cbo.gov/sites/default/files/cbofiles/attachments/06-07-ChangesSince2001Baseline.pdf

One may convincingly argue for reduced taxation, and certainly should do so when considering the growth of spending versus the need for more revenues, but the reality of tax cuts, from Reagan through GW Bush, is that nearly half of the American people have been taken off of the federal income tax rolls altogether. Taxation is thus now an argument between the upper half of the middle class and the rich.

There is no evidence that reducing top marginal rates alone will now increase revenues to the federal treasury. If that is to happen, rates can only be lowered if the tax base is widened, which means the elimination of loopholes and deductions. We may recall that we did exactly that, along with rate reductions, under Reagan. The Laffer curve relies upon taxpayers finding it easier, if not completely economically advantageous, to pay the income tax versus seeking to shelter income from taxation. Those calling for a "soak the rich" policy have on their side of the argument the fact that, regardless of tax rate, the effective tax rate for the rich is far lower than the 39% on the books. Eliminate the deductions that make it so and you've an argument for lowering rates. Let them remain and you run hard up against those CBO numbers that show no increased revenues received.