The savings rate is an important contributor to economic growth because surplus permits investment.

However saving can hurt growth by reducing consumption.

Savings can be thought of as a steady state rate of saving that the economy has adjusted for. Saving is a higher order effect that causes an increase in the savings rate, temporarily depriving the economy of the level of consumption it expects.

I'm curious what portion of new investment goes into IPOs, additional issues, VC, etc., compared to the portion that just changes hands between fellow 'savers'.

If I buy $1mil of MSFT, I didn't contribute a cent to their payroll. I didn't create jobs, or grow anything. I just transferred $1mil to another investor, who will probably use that money to invest in AAPL.

Seems to me a huge portion of investment is just moving money around a relatively closed system akin to sports betting.

By buying $1mil of MSFT you helped set the market price for their stock and therefore value the company. Based on that value Microsoft can then go to the market and raise new capital.

That is presuming that MSFT ever issues more stock. They haven't appreciably done so in the past 15 years, and the same trend applies for most of the DOW.

If MSFT never issues more stock, what then? Furthermore, helping to determine the value for possible future issuance seems like a very marginal benefit relative to the overall volume of stock trading.