Specifically declining quality of life in regards to what is actually available as a potential quality of life.

Married couples making $45,000 a year both working full-time jobs and having capped out their potential income for the foreseeable future are not the kind of people who typically want to have kids.

On the flip side, in the middle class, married couples making $85,000 or $100,000 a year have a vast awareness of how little distance twice the income of their poor neighbors makes in their quality of life and are also starkly aware of how difficult things would be if a spouse had to stop working in order to raise the child, even for half a year.

Jobs not paying enough for a single person to support a family of three is the primary reason why people do not want to have kids.

Secondary to that is the extraordinary cost of owning a home. Most renters do not necessarily want to add a child into their one-bedroom apartment.