Markets Insider: Retail investors are about to throw in the towel and finally sell if Apple and Tesla stumble, Vanda Research says

The firm estimates that combined, Apple and Tesla account for 34% of the average retail investors' stock portfolio. That concentration has actually helped retail investors performance, as both Apple and Tesla have outperformed the S&P 500 considerably year-to-date and over the past year.

Vanda believes the outperformance has been driven by Apple's status as a defensive, high quality company favored by institutional investors, while Tesla's meteoric rise over the past few years has attracted a large retail shareholder base and has led institutions to be weary of shorting the electric vehicle maker.