NEW YORK ( TheStreet) -- The list of retailers still reporting monthly same-store sales figures is slowly whittling down. Starting in August, just 22 companies will release the figures, begging the question: Has the sample size become too small to analyze?

Hot Topic ( HOTT) will be the next retailer to go mum, moving to only reporting quarterly numbers starting in the third quarter.

The teen retailer is following in the footsteps of its peers, with Abercrombie & Fitch ( ANF), Aeropostale ( ARO) and American Eagle Outfitters ( AEO)also discontinuing the practice earlier in the year.

BJ's Wholesale ( BJ) also will soon disappear from the list once it is taken private.

The trend of abandoning the monthly sales practice is clearly in vogue among retailers. Behemoth Wal-Mart ( WMT) hasn't reported monthly same-store sales numbers for more than a year, while Children's Place ( PLCE)and American Apparel ( APP) also went quiet in 2010.

Big-box giants Sears ( SHLD), Home Depot ( HD)and Lowe's ( LOW) have been absent from the whirlwind for years.

And none of the pure women's apparel players -- Ann ( ANN), New York & Co. ( NWY), Chico's ( CHS) -- abide by the practice.

Currently, in fact, comparable-sales reports only represent about 10% of total U.S. retail sales, according to Customer Growth Partners, and really primarily portray only two retail sectors -- apparel chains and department stores.

"Monthly sales are a skewed look since they are so mall- centric and apparel-centric, which is a small part of the market," says Craig Johnson, president of Customer Growth Partners. "Entire sectors are left out, including consumer electronics and home improvement. These are giant sectors."

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 is friendly or unfriendly.

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 down 1.6% with stocks like Kohl's ( KSS), Buckle ( BKE) and Zumiez ( ZUMZ) taking a beating.

But how good of a gauge on the health of a company or the sector 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, as they did in July to clear summer merchandise to make room for back-to-school, 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 or even a warmer 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.

There's a mix among the group of those who include online sales in their results and those who do not incorporate the figure. Macy's ( M), for example, reported a 5% jump in July same-store sales, but this included a 36.7% surge in online sales.

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), as wells as teen retailers Zumiez ( ZUMZ) and Hot Topic ( HOTT), traditionally release their numbers ahead of the pack.

A better gauge of the overall retail sector is the Commerce Department's monthly retail sales, which includes data for sporting good stores, hobby and books and other divisions not represented in same-store sales, Wall Street Strategies analyst Brian Sozzi said. He also said to look at other economic monthly data like consumer credit to get a clearer picture of the health of the consumer.

Still, Sozzi doesn't believe monthly sales reports should be done away with altogether.

"I use to think there was a benefit for retailers to move away from reporting monthly results since it often causes volatility in the stock, but your taking information away from investors who are use to having these numbers," he said.

- Reported by Jeanine Poggi in New York.

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