While the sector is in a multi-year slump, its depth is masked because of chains' short-term focus. On quarterly conference calls with Wall Street, managements often cite external factors -- higher gasoline prices or the weather, for example -- for how they did in the past three months or so.

What they don't talk much about is the longer-term attractiveness of their restaurants to potential patrons. A look at cumulative numbers from several years helps explain why.

In some cases, national brands have lost more than 10 percent of their customers -- a deep hole from which to emerge. Such losses point to chronic erosion that can't be blamed entirely on external factors.

For example, Applebee's International Inc., the world's largest bar-and-grill operator, reported a 6 percent to 6.5 percent decline in guest traffic in August from a year earlier. But the 2006 number had been 2.5 percent to 3 percent below that in August 2005, and the 2005 number was off 4 percent to 4.5 percent from 2004. Finally, guest traffic in August 2004 had been down 1.5 percent from 2003. So cumulatively, the chain's traffic last month actually had fallen between 14 percent and 15.5 percent over the past four years.

Applebee's, which is awaiting shareholder approval of its sale to pancake-house operator IHOP Corp., is among the worst-performing major casual-dining chains. It has reported falling guest counts in 34 of the past 37 months.

But some competitors aren't faring much better. Chili's Grill & Bar, the flagship of Brinker International Inc. and Applebee's biggest rival, incurred an 8.7 percent falloff in patronage from July 2003 through this past July. The multi-year total for August could easily exceed that; it was down 12.2 percent from August 2004 through August 2006, but Brinker hasn't yet reported last month's results.

Such figures led Goldman Sachs restaurant analyst Steven Kron to advise clients Thursday to avoid bar-and-grill stocks, given the crowded market and a lack of differentiation.

Another Brinker chain, Romano's Macaroni Grill, has a cumulative traffic decline of 18.4 percent from July 2003 through this past July, according to J.P. Morgan Securities calculations. That may help explain why the 230-unit brand is up for sale.

Some chains don't report guest count changes at all, so analysts make educated estimates. Often they do so by subtracting the average menu price increase, or average change in guest check size, from same-store sales. For example, if a chain reports a 4 percent same-store sales increase in the same period it raised prices 5 percent, it may well have had a 1 percent decline in guests.

That realization can be important for investors. In reporting July results for Cracker Barrel Old Country Stores, owner CBRL Group Inc. said that same-store sales were up 1.6 percent. But that seemingly encouraging figure requires some context. CBRL noted that during the period the average guest check was about 1.9 percent higher "due to an average menu price increase of about 2 percent."

So while comparable sales rose, guest counts were actually down -- about three-tenths of 1 percent, J.P. Morgan told clients.

What's more, since fiscal 2003 guest traffic for July was down 7.8 percent, the brokerage concluded. Such a decline is especially significant for CBRL during that month because many of its Cracker Barrels are located along interstate highways so as to attract vacationing motorists.

Chains that don't publish regular guest traffic numbers include Cheesecake Factory Inc., Panera Bread Co., P.F. Chang's China Bistro Inc. and Ruby Tuesday Inc.

However, P.F. Chang's used directional descriptions -- "decline in overall guest traffic" and "slight decline" -- in its most recent quarterly report filed with the Securities and Exchange Commission.

As for what accounts for the widespread falloff in casual dining's popularity, a recent survey by the Dublin, Ohio, consulting firm WD Partners found a variety of reasons. Many of the 1,000 people interviewed cited "eating healthier." Other explanations included higher gasoline prices, unplanned expenses and household debt levels and "tired of the same old chains."

Commenting on that last reason, WD Partners' Dennis Lombardi wondered, "Have chains been too slow, or too conservative, in evolving their concepts? ... Maybe the megabrands need to focus on innovation to catch up with consumers."