Passing a large unpaid for
tax cut 7 or 8 years into a recovery is just plain reckless. Real
tax reform that is basically revenue neutral would be another story.
Gross domestic product (GDP) growth comes from two main sources: 1) growth in the labor force and 2) growth in productivity.
LABOR FORCE GROWTH
The economy is already running at or near full employment. It’s true that the labor
participation rate is at a relatively low at 63%, down from 66.4% in January 2007. However, the aging of the U.S. population leaves little hope of reversing the trend line.
The most recent increases in the workforce occurred in the 1970s through the 1990s, with the entry of baby boomers and women. But the baby boomers of both sexes are retiring now. Unless immigration is drastically INCREASED the U.S. workforce will continue to shrink at least for the next 15 to 20 years.
PRODUCTIVITY GROWTH
That places the onus on productivity growth. The biggest driver of productivity growth is technological change. However, as an advanced economy all the "low hanging fruit" of technological innovation for the U.S. is
BEHIND us. Read Robert Gordon (Northwestern Univ.) who has written extensively on this matter.
https://press.princeton.edu/titles/10544.html
The last time we grew above 4% was during the 90's when the gains from Info. Technology were being felt. Smart phones, Uber and Driverless cars are simply not as impactful innovations as say running water, the internal combustion engine or the initial wave of computer technology were during earlier decades in our history.
The U.S. is a really large and complex economy, and taxes are a relatively small part of the picture. They are certainly not unimportant. But even an absolutely perfectly crafted
tax reform package would only add a miniscule amount to GDP growth.