The middle class has seen their income grow, but their ranks have shrunk.The Good Brigade/Getty Images The middle class is often a topic of discussion among politicians and economists. But who makes up the middle class? It's a group that's been shrinking over the decades. To be middle class as a single American, you have to make about $30,000 to $90,000. If you've listened to any politician — or just President Joe Biden's speeches — you've heard about the middle class.Indeed, most Americans have said that they're part of the middle class.