Understand the 800-Pound Gorillas in the S&P 500

By Daniel Jordan Photography @Shutterstock

OK, this stock market is top heavy. Remember, you buy the stock market when you buy a 500 index. But do you know how that index works? Look at the S&P 500 for example. Sure, it’s 500 stocks, but about a third of the index is dependent on five companies. Why? Because it’s a market cap weighted index meaning the size of a company, its market cap (price times shares outstanding) dictates its influence.

“Remember when a trillion dollars was a lot of money?” asks Spencer Jakab in The Wall Street Journal’s Heard on the Street feature, “Gigantic Stocks Are a Reason to Worry.” Five companies have reached that level recently. And look at Apple. Its market cap is approaching $3 trillion. What does this mean? “The precedents aren’t encouraging,” explains Jakab and he continues why, here:

One ob­vi­ous rea­son is that even pas­sive in­vestors are in­creas­ingly bet­ting on just a hand­ful of stocks vul­ner­a­ble to a dud prod­uct or reg­u­la­tory set­back. Think­ing of it in terms of buy­ing an en­tire busi­ness is help­ful: Would you rather own the iPhone maker or all of Mc­Don­ald’s, Wal­mart, AT&T, Philip Mor­ris, Berk­shire Hath­away, Proc­ter & Gam­ble, JP­Mor­gan Chase, Star­bucks, Boe­ing, Deere and Amer­i­can Ex­press com­bined? A lot would have to go wrong all at once to tor­pedo that di­ver­si­fied group of blue-chip stocks.

Action Line: This is a top-heavy market where you need to ask yourself how many iPhones can Apple really sell? Invest every dollar like it’s your last. And invest in terms of thinking about having that dollar buying a business.