In this series, we take a look at the 25 stocks on the S&P 500 Index (SPX) that have turned in the worst performance during the past decade -- what went wrong, and what happens next.

New York-based Interpublic Group of Companies (NYSE: IPG) is a marketing services firm, but they're not your average PR hucksters. Flip through IPG's resume, and you'll find that they were once tapped as the "brand steward" for Coca-Cola Classic. Is there a more solemn task in the world of marketing? Perhaps -- Coke also handed IPG the reins on Cherry Coke, but jealously guarded its Sprite brand from the mega-marketer's grasp.

What went wrong? At number 22 on our list of SPX underperformers, IPG lost 72% of its value from June 30, 1998 through June 30, 2008. The worst of the stock's woes occurred during the first several years after the turn of the millennium. A broad economic slowdown led many clients to trim their spending on advertising, and -- as one of four "megacompanies" that essentially ruled Madison Avenue -- IPG couldn't help but feel the pinch.

Even as the marketing behemoth faced down this fundamental challenge, an accounting fiasco caused the company to restate six years' worth of financial results. Interpublic soon found itself facing a formal investigation by the Securities and Exchange Commission, along with an IRS audit over the small matter of $41.5 million in unpaid taxes.

By May 2003, the company was so shamed by its financial failings that a slew of top executives agreed to forfeit their stock options to appease shareholders and lower-level employees. Oddly enough, investors later learned that IPG managed to pay out more than $41.4 million in bonuses to its top executives in 2003 (incidentally, that was a year in which the firm lost $451.7 million).

And what about Coke? The world's best-known brand, realizing its instinct about Sprite was correct, snatched the plum Coca-Cola Classic assignment away from IPG unit McCann-Erickson in 2003.

What next? Interpublic may have lost "the real thing," but it's now in league with another American icon -- Jay-Z. The self-proclaimed "best rapper alive" teamed up with fellow entrepreneur Steve Stoute in early 2008 to form Translation Advertising, a unit of IPG's Translation Consultation. However, Interpublic can probably relate on a deeper level to its new mascot for client MasterCard: the infamous Saturday Night Live character Mr. Bill, who's certainly no stranger to crushing blows and lingering pain. In the meantime, stay tuned for the company's next turn in the earnings spotlight, which is scheduled for July 30.

Elizabeth Harrow is an analyst and financial writer in the research department at Schaeffer's Investment Research. She is featured in the weekly video series Option Basics on SchaeffersResearch.com.