Gartner concedes the progression represents his own experience and lists the following phases:

1. Local restaurants, started by great chefs.

2. Larger format restaurants that represent more of an investment and draw a larger audience from a larger geographic area. They include expansions by local restaurateurs and regional and national chains.

3. Locally owned specialty retail shops, including art galleries.

4. National retail chains.

"National retail doesn't move in until an area is proven," Gartner says. Once national retailers arrive, the rental rates begin to climb, and an evolution takes place in which the local retailers are often driven to an adjacent area, potentially repeating the cycle. "Not all areas make it through all four phases," Gartner also points out. "Some get stuck along the way."

Without completely discrediting Philadelphia's current Center City residential boom's contribution to expanding retail here, Gartner says, "residential development is great for downtowns, but it is not the opening lure to downtown shopping. Construction of multifamily housing for as many as 1,000 or even 2,000 people, which is ambitious for many mid-size cities, doesn't create nearly a large enough market to support retail," he reasons.

He gives a large measure of credit for what he calls "Philly's retail renaissance," to Stephen Starr, a local restaurateur who initiated a competition for quality restaurants here in the early 1990s and now owns more than a dozen. Paul Levy, executive director of Center City District and Central Philadelphia Development Corp., confirms a virtual explosion of restaurants here over the past decade, citing a 206%-increase in eating establishments since 1992.

Starr began his empire with Continental Restaurant & Martini Bar in the then-newly gentrifying Old City section of town. It quickly became a gathering place for the young and hip, and Old City has since become a mecca of art galleries and trendy home fashion and furniture stores. Starr capped Old City with his much larger and pricier Buddakan restaurant. Then along came Starbucks.

Center City's priciest retail occupies a five-block section of Walnut Street, from Broad Street to Rittenhouse Square. Coach, Bebe, Deisel and other upscale national retailers recently joined Tiffany and Burberry there. "While a few local stores got in under the wire and can maintain their rent for now," Gartner predicts this shopping strip will soon become "the sole domain of national retailers, because they can afford the rising rental rates and have credit ratings to prove it."

Hence, here comes the parallel stretch of Chestnut Street, which was devastated by the demise of Bonwit Teller in the early 1990s, an exit that was compounded by a devastating 38-story office building fire that left its charred remains exposed for several years. Chestnut Street is now entering Gartner's fourth phase of retail development.

"Two words, Stephen Starr, are responsible for the Chestnut Street retail renaissance," Gartner says, referring to Starr's recently opened Continental Mid-Town restaurant that signaled its arrival with a five-foot olive marquee, stabbed with an equally oversized toothpick. Borders books left Rittenhouse Square for a renovated bank building on Chestnut across from the Ritz Carleton, and Tower Records and CVS Pharmacy now occupy buildings at the eastern end of the five-block shopping strip.