A cash incentive in other places may not work but it’ll definitely work in India. Most of the country is still poor, offering $100 per child will drastically increase the birth rate, at least in the short term.

Of course this doesn’t incentivize the right people to have kids, but population grows none the less.

A state in India is already trying to implement this (https://www.hindustantimes.com/india-news/why-andhra-pradesh...), $300 for 3rd child and $400 for 4th child.