A year ago I posted about a record $7.4T cash on the sidelines. It's now ~$8.4T and the S&P 500 is up 15%+

[Post from a year ago](https://www.reddit.com/r/stocks/comments/1na2xhp/record_74_trillion_in_cash_on_the_sidelines_will/)

A year ago I posted in this subreddit asking if the record $7.4 trillion in money market funds would act as a safety net or "dry powder" to catch a dip.

Some of the replies essentially told me that cash on the sidelines is a myth either because every stock purchase just hands cash to a seller or because the vast majority of that money belongs to corporate payrolls and retirees happy collecting 4-5% risk-free.

Checking FRED today, total MMF assets are up over $8.4 trillion and the S&P 500 has climbed another 15%+ from 1 year ago.

If this cash isn't fueling the stock market and equity gains aren't draining the cash pile, what's driving both to all time highs simultaneously? Is it literally just compounding yield and general money supply expansion or is there something else going on under the hood?