Stem Tower is completely removed from the pyramid for the main reason that its continued success is more connected to the Nexus than anything happening in Stem City. It still has to make sure its higher classes are satisfied enough with the economy to not attempt a revolution, but other than that, If the population were to drop to single digits, Stem Tower could live on.
However, there are those who won't let that happen. They need the number of Stem Rams constantly growing, growing, and growing.
The noble higher class consists of a few extremely wealthy families, such as the Fries, Von Voldarks, and Von Solstars. They control roughly 90% of the city's Marks.
About 25-40% of the middle class owns or is invested in some sort of business. The rest of them partake in the workforce directly.
The 35% unemployed are made up of a majority of homeless people forced to take inconsistent, temporary jobs or steal to survive.
Outlanders are about as poor as Stem City's lowest classes, but they are effectively completely removed from the wider economy due to an almost universally shared cultural disdain for and repulsion of Stem City's class system and economic practices. Any noble business trying to set up shop in the Outlands is forced out in one way or another.