Institutional investors represent 90% of stock market trading volume,
generally possess hundreds of billions of Dollars in assets, and
aren't motivated to "get rich quick" since they already have plenty of
money.
Institutional investors include everybody who has pension money, retirement fund money, and non-retirement money in mutual funds and ETFs. This is all in addition to those funds linked to insurance companies, University endowments, and other financial companies.
While tho money directed by the mutual fund is large, the investors can have small sums invested. Those investors range in age, income, and goals.
Even money designated for retirement can be day-traded. In the United states there was a not-insignificant number of government employees who were day-trading their TSP funds.
This is in contrast to the individual investor who would be solely
motivated to get rich quickly and thus would be making frequent
high-risk trades.
While an individual investor is skipping the big funds, they can still buy and hold.
From the S&P 500 chart, we can see over the last month it has gone up
and down between 5221 points and 5375 points. For this up and down
ripple to occur, clearly institutional investors have been selling and
buying very frequently, much like a day trader would.
The value of the S&P 500 index will change everyday the markets are open. If even one person or mutual fund buys one share in a company it's price could change.
My question is why? Why would they make these short-term adjustments
when their assets are worth hundreds of billions of Dollars? What are
they doing with the cash from selling in the meantime?
Even big funds have to buy shares. When employee and company match funds hit the 401(k) there will be shares purchased to invest those funds in the market. When employees move money within their account shares will be bought and sold. When people cash in their retirement money shares will be sold. All these actions can impact the value of the index. The same thing happens when the makeup of the index changes.
What do they do with cash when shares are sold? They invest it in different companies.