There are two ways to look at the middle class: 1. The actual statistical average or median whatever that number happens to be is the middle class, full stop.

There are two ways to look at the middle class: 1. The actual statistical average or median whatever that number happens to be is the middle class, full stop. 2. The middle class is the ideal standard of living one should expect for people who are neither rich nor poor. I happen to subscribe to the latter philosophy. The middle class is whatever range of incomes it takes in a given city adjusted for cost of living to own a modest home and save significantly for retirement. SF's median income can't do that. That used to be how we defined the middle class a generation or two ago, back when home ownership and solid retirement plans were more common. Nowadays it's less common to make enough income to support that lifestyle in many cities and people who can afford it are being increasingly referred to as rich.