Having Children

Anecdotaly, it seems like the lower the income level of a society or sub-society the higher the birthrate. Maybe that can be explained by the fact that man has an innate desire to be עוסק בישובו של עולם. If a person is building, creating, changing, making goods, performing services to help the world then he doesn't revert only  to the basic almost animalistic desire to have children. However, the less other עוסק בישובו של עולם a person is, the more he needs to have children to be מקיים לא תוהו בראה לשבת יצרה.

A person's measure of עוסק בישובו של עולם can usually be measured by his earnings over time. For sure on a larger sample size. We all feel the need to pitch in, the question only is, how?