Apple's Size Clouds Market

In analyzing US corporate earnings and stock-market trends, apples-to-apples comparisons may now require tossing out the Apple.

Apple's success selling consumer gadgets has pushed its share price above $500, cementing its place as the U.S.'s largest company, with a market capitalization of $475 billion. But its gargantuan size is making it difficult for Wall Street to get a big-picture view of the earnings and margins for other American corporations. As a result, some equity analysts are cutting Apple out of the frame—and finding a dimmer outlook for the broader market.