Watch out?

No $20 bills on sidewalks is pretty clear. Also clear is the logic of the efficient markets hypothesis (EMH):  in the race for profit, new information is quickly scooped up and acted on -- and "baked into" asset prices. (To be sure, EMH is also misunderstood by many who bizarrely expect any and all surprises to also be reflected in asset prices.) Also clear is evidence that many investors have accepted the logic of the efficient markets hypothesis and have moved their holdings from stock pickers to index funds.

Stock market prices are the original "big data" -- and an unavoidable temptation for study by finance experts. Slightly less expert are those who look for portentious episodes in daily life (business and other).  Joe Kennedy supposedly got out of the stock market just before the 1929 crash because his shoeshine guy tipped him to buy.

This morning's WSJ includes "Does Anyone Remember How to Make a Subprime Mortgage? ... Brokers willing to learn the lost art of making risky mortgages are in demand again."  Your mileage may vary -- and there are many mortgage markets in the U.S.  But mortgage originators have been able to sell the mortgages they make. And the U.S. government GSE's (Fannie and Freddie) and others who buy them have been known to get bail-outs when things do not work as planned (wished for).

The usual caveats apply.