As you know, the rationale for supply side economics (give tax cuts to the wealthy) is that those who benefit will use that money to  invest in capitol and make jobs. That hasn't worked, ever, and especially in an economy that lacks consumer demand. So corporate beneficiaries park their money in safe accounts with near-zero returns, and delay investment in moribund markets. Demand side investment would be jobs stimulus such as national infrastructure projects, which would create a million good jobs, increase revenue, and lower deficits. The work itself would be an investment with returns generally thought to be 1.5 to 1, and our infrastructure sorely needs renewal.

Our consumer saving goes into low-return accounts. Long-term saving primarily is into funds and into payroll taxes, which fund government spending, allowing tax breaks mostly for the wealthy. It could change, but Trump and Ryan have both promised cuts for corporations and the wealthy.