This plot of cuisine type versus age shows not only how old each Inner Sunset restaurant is, but over what duration the current restaurants of different types were opened. Thanks to long-lived Pasquale's and newly-minted Baiano's (replacing Milano's Pizzeria), Italian and pizza places have the widest spread — 55 years. Conversely, the corridor's three Thai places all opened within seven years of each other. And the Sunset's youngest Thai spot, Baan, is already more than four years old. Has a brief moment for opening Thai restaurants already come and gone?
About a third of the commercial district's restaurants fall evenly into one of two broader categories — "Bakeries & Desserts" and "Sandwiches, Burgers & American". These categories share several attributes: there are 12 businesses in each, the oldest in each category opened in 1995, the newest opened in approximately the last year, and businesses in these categories have been opening almost constantly throughout the last 20 years.

Taking a closer look at the types of services offered in the Inner Sunset, some observations are familiar. Like Divisadero, there are quite a few hair and nail salons — a total of 9.5 percent of Inner Sunset businesses are related to beauty.
Similarly, the oldest single category in this district is that containing various repair, automotive, and construction services. In the Inner Sunset, these businesses average a mature 36.6 years (comparable to Divisadero's automotive services average). Standard Roofing Co opened in 1952, and Pierre's Auto Body started at 1223 9th Ave. in 1967, annexing another space a block away in 1989 when the previous mechanic decided to close up shop.
Out-aging every business in the district, service or otherwise, is Sunset Shoe Repair. It likely services a lot more individually-toed barefoot running shoes these days, but it claims to have been in continuous operation since the turn of the previous century, 114 years ago.
Among the newer services are a small handful of software companies and tiny startups centered near the Victorian home that served as Craigslist HQ until 2010. Sutro Software's 9th Avenue office is eye-catching from the street because its balcony boasts one of
these.
Unlike other neighborhoods we've looked at so far, the Inner Sunset has turned itself into something of a center for health and wellness. Between medical offices (like dentists and optometrists), mental health and counseling professionals, and wellness and alternative medical services like an abundance of chiropractic, massage, nutrition, acupuncture, and Chinese medicine practitioners, health-related services make up 15 percent of the total businesses in this district.
These para-medical services range in age from the older cohort — Sunset Dentistry and psychologist Janet Endelman started in 1994, Irving St. Chiropractic in 1991, and Pacific Rims Optometry in 1989 — to the very new crop — like Park Smile and Helix Acupuncture from 2012, Liam Tarpey Massage from 2013, and Olga Rocklin Psychotherapy this year.
If you include fitness under that umbrella of health and wellness, then gyms, yoga and pilates studios, and personal trainers bump the percentage up to 17 percent of the total businesses in the area (and 34 percent of service businesses). Moreover, these numbers are likely underestimates. Our standard for inclusion in this storefront investigation requires that the business be apparent in some way from the public street, but many of the health and wellness practitioners leave their businesses completely unmarked for privacy's sake.
Why might this health emphasis arise? Perhaps it's thanks to the neighborhood's position at the foot of UCSF's Parnassus campus and Medical Center. UCSF Parnassus opened in 1898 and became well-known after caring for many victims of the 1906 earthquake. Here's
what it looked like in 1908 (pre-
Sunset Tunnel).
Perhaps drawn in first by the hospital, medical offices in the neighborhood are an older bunch, averaging about two decades of operation. Most of their alternative medicine neighbors, as well as therapists and fitness services, arrived much later to flesh out and diversify the burgeoning health and wellness scene. On average, those businesses are only half the age of the medical offices, but three times as plentiful.

So how has this commercial corridor changed over time? It's hard to say with certainty when we only have access to complete data on what's here right now. But breaking the current businesses into cohorts by age and examining the composition of each age group, we can shed a little more light.
As it turns out, the lasting businesses from before 1995 look a lot like the ones from the past three years (and also the ones from middle cohort, 1996 to 2011). It appears that there was a small shift two decades ago toward more restaurants and fewer services and non-apparel retail. The (tiny) share of apparel retail is slowly increasing — but whether that indicates a real shift toward more clothing stores as in some parts of town, or simply the shorter relative lifespan of fashion, is up for debate and further study.
The consistency of these age cohort snapshots suggests an inertia to the make-up of the Inner Sunset. Whether geography, topography or demography is most responsible, there's a sense that this neighborhood has been independent — largely self-contained and self-sufficient — in meaningful and measurable ways throughout its lifespan.
We'll be doing more analysis of our neighborhoods in the coming months, and using this research to inform our daily coverage. Please let us know in comments if you have ideas.