For what it's worth "Upper middle class" is a pretty widely used classification. I couldn't give a technical definition and don't even know if one exists, but as someone a little younger it's always seemed like a semi-cohesive group. People who are able to attend private schools and $160/4 year college programs, whose parents can float them a little if needed, who have a certain range of hobbies (e.g. yoga, skiing), who wear a certain range of fashion brands, who typically live in certain neighborhoods of cities. Some of those properties on their own don't define the group, take it as a whole. It's basically where your family is doing well and set you up with a lot of opportunities, but you're not extremely rich and you still have to work. It's most people I went to university with (which is a competitive, expensive one), and it's most people I know paying market rate rent here in SF.