ever wondered why Poor countries tend to population increases whereas rich countries with abundance of basic resources tend to have low/negative population grow

ever wondered why Poor countries tend to population increases whereas rich countries with abundance of basic resources tend to have low/negative population growth? here is your answer: http://www.physicsoflife.pl/dict/calhoun's_experiment.html http://www.physicsoflife.pl/dict/calhoun's_experiment.html