Sachs argues that the Malthusian prediction (the rate of population increase would outstrip the rate of increase in output) has not been true so far because of tremendous increases in output per capita (due to technology breakthroughs).
However, he warns:
… it could be argued we have not really found a way to solve the Malthusian problem. We have thus far only managed to feed the globe’s growing population through mining of raw materials and sources of energy. We all know this cannot continue forever – some sources will run out and others will damage the earth beyond repair.
And, more more need of Keynesian policies in Africa:
Keynesian spending plans could be used to provide a massive investment of infrastructure to Africa that would set the continent on its way to development.