Of course the S&P 500 has been growing, central banks are buying stocks left and right. What's worth mentioning is that both governments and companies have massively increased their debt during that period, so its really hard to judge what the 250% S&P 500 growth means.
The S&P 500 growth means that companies are confident enough in their future cash flow that they will borrow money against that to buyback their own stock. This has been a trend since the 80s.
We are living in situation where, instead of competition driving profits down to 0, or profits being used to finance investment and growth -- profits are simply returned to shareholders. Low interest rates are only reinforcing this. It's a great time to be a shareholder, and not a great time to be a consumer.
Alternatively, it means that executives that are mostly incentivized by short-term stock price movements via option grants have found a way to juice their compensation.
The S&P is growing because companies are borrowing to buy back their stock. It is illegal stock manipulation but that law is no longer enforced. This makes money that used to be taxed as dividends eligible for capital gains treatment and it taxed at a lower rate than it would be as dividends. this lowers tax income to the government. A downward spiral with no end in sight.
