Today the top five S&P 500 companies — Apple, Amazon.com, Google, Microsoft and Facebook — combined are worth $4.095 trillion versus $4.092 trillion for the bottom 282 companies. While this might seem mind-boggling, this sort of concentration is normal. In 1965, AT&T Inc. and General Motors Co. alone represented 14.5% of the S&P 500. What is different today, however, is that all the big players are tech names. For many of our clients that have been granted Restricted Stock Units in these companies, which have now settled into shares, a new financial planning challenge has been created, managing concentrated stock risk.