Dynatrace Inc. $54.41-2.01-3.56% ...

The richest person in the world just hit an even higher milestone. Elon Musk’s net worth has reached $400 billion, according to Bloomberg, making him the first person ever to cross that mark.

The S&P 400 MidCap Index tends to go further down the market-cap ladder, favoring small cap stocks that tend to be more volatile than more established mid-cap stocks. Small-cap companies ...