Who said this?

Still so very true today as it was 47 years ago. Why people believe otherwise is mystery to me.....

Tax reduction thus sets off a process that can bring gains for everyone, gains won by marshaling resources that would otherwise stand idle—workers without jobs and farm and factory capacity without markets. Yet many taxpayers seemed prepared to deny the nation the fruits of tax reduction because they question the financial soundness of reducing taxes when the federal budget is already in deficit. Let me make clear why, in today's economy, fiscal prudence and responsibility call for tax reduction even if it temporarily enlarged the federal deficit—why reducing taxes is the best way open to us to increase revenues.

—President John F. Kennedy,
Economic Report of the President,
January 1963