> If one wants a counter argument to "too many people for the economy" one can start here : https://www.jstor.org/stable/2523702?seq=1

Or you can just point out that, well, if there are too many people, just (virtually) split the country down the middle: voila, fewer people in the country.

A more sophisticated argument brings up density. But it's usually the sparsely populated parts of a country that are poorer.