(Updated with American Eagle Outfitters monthly sales announcement.)

NEW YORK ( TheStreet) -- American Eagle Outfitters ( AEO) ( ANF) is piggybacking off rival Abercrombie & Fitch, announcing on Thursday that it will refrain from reporting monthly sales results come 2011.

The news comes after Abercrombie & Fitch announded earlier in the month, following lackluster October results, that it too will no longer report monthly same-store sales numbers starting next year.

Neither Abercrombie & Fitch nor American Eagle provided a reason for their decision.

The move to discontinue reporting monthly figures is in vogue with retailers, who are exposed to wild swings in their stocks after the numbers are released.

Retail giant Wal-Mart ( WMT) stopped reporting monthly sales back in June, while Children's Place ( PLCE) and American Apparel ( APP) also went mum in earlier this year.

Sears ( SHLD), Home Depot ( HD), Lowe's ( LOW) and Chico's ( CHS) are also among the companies that no longer report monthly same-store sales.

Currently, in fact, comparable sales reports only represent about 10% of total U.S. retail sales, according to Customer Growth Partners. "The monthly reports Wall Street so breathlessly awaits really primarily portray only two retail sectors, apparel chains and department stores, each of which represent well under 3% of U.S. personal consumption expenditures," Craig Johnson, president of Customer Growth Partners said in a statement earlier in the year.

"As we have stated for some time, refraining from monthly comp reporting is a good way to align how management thinks about the business to the interest of long-term shareholders," Wall Street Strategies analyst, Brian Sozzi, wrote in a note.

Retailers are not required to report monthly sales and it's an expense to do so. For apparel retailers, in particular, it often adds significant volatility in the stock if a month of weather or calendar shift if friendly or unfriendly, Sozzi notes.

"Specifically to American Eagle, it has been undergoing a fundamental change to planning and allocation that began in fall 2009, a process that does not produce results overnight, and earlier in the year led to inconsistencies in the business," Sozzi continued.

Despite the shrinkage in the number of companies that report monthly same-store sales numbers, the extent to which investors scrutinize these numbers has increased. Today alone, the S&P Retail Index is currently up 1.5% to 480.22, with stocks like Gap ( GPS), Zumiez ( ZUMZ) and Ross Stores ( ROST) all rallying about 5% on their results.

But how good of a gauge on the health of a company are these numbers, really?

The two biggest factors contributing to same-store sales upside and downside are price and the number of customers who purchase merchandise. Thus, if prices go up and the number of transactions remains the same, comparable sales will increase, and vice versa. Any time comparable sales rise it means shoppers are either buying more or spending more -- or both, which, of course, is a good sign.

But when retailers offer discounts and shoppers close their wallets, as seen during the economic downturn, same-store sales can take a major beating.

Retailers have come up with some excuses to shift the blame for declining monthly sales away from internal operations. The two most frequently used (read: overused) are the weather and "calendar shift." A colder summer, a hotter winter, a few wayward storms -- all are used by companies to explain why shoppers stayed away from their stores.

In the same way, an extra shopping day in a month or the shift of a holiday earlier or later are also (and with more legitimacy) tied to sales increases or decreases.

Another caveat: While same-store sales are a good measure by which to judge a company against its own past performance, they don't truly present an accurate yard stick for stacking up retailers against each other. There is no official set of standards for how retailers should report comparable sales, since it is done on a voluntary basis.

Most retailers exclude online sales in their tallies, but Macy's ( M) and Kohl's ( KSS), for example, includes the figure, generally inflating its results.

In October, Macy's reported a 2.5% uptick in same-store sales. Included in this tally was a 19.7% surge in online sales. **Macy's was swayed back into reporting same-store sales figures after it announced it would discontinue the practice.**

The only standard (mostly) agreed upon, is the reporting calendar, which is compiled by the National Retail Federation. But even this schedule is not a hard-and-fast one, as drugstores like Rite Aid ( RAD) and Walgreen ( WAG), and teen retailers like Zumiez ( ZUMZ) and Hot Topic ( HOTT), traditionally report their numbers a day before the rest of the pack.

A better gauge of the overall retail sector is the Commerce Department's monthly retail sales data, Scott Krugman, vice president of public relations at NRF, told TheStreet earlier in the year. Yet these numbers are only covered superficially by most reporters and analysts.

Still, this doesn't mean monthly sales reports should be done away with all together. "The more information out there for the investor is always better," Krugman says. "Monthly sales have value, but they are not the be-all and end-all; they are only part of the story."

--Written by Jeanine Poggi in New York.

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