If every single person decided to invest in index funds on the same day, would it be theoretically possible for EVERY stock in the S&P 500 to drop and for $VOO to rise?

I know it would never happen like this, I'm just trying to grasp the concept.

It appears to me that, since ETFs are traded on the market like common stocks, their share price do not entirely reflect the value of the underlying assets.

EDIT: "Because an ETF trades like a stock, its price will fluctuate during the trading day, due to simple supply and demand. If many investors want to buy an ETF, for instance, the ETF’s share price might rise above the value of its underlying securities." http://ift.tt/2s8gWtq

Submitted August 18, 2017 at 05:46PM by NewAccountingKid http://ift.tt/2xcuF2i