In a malthusian model, show how the demographic response to higher incomes after a one-off technological improvement ultimately reverses any gain in incomes (the malthusian trap).

Based on theorems developed by Thomas Malthus, a technological improvement leading to higher incomes will reverse any gains in income because as the standard of living increases (due to the new technology), the need for a higher income also arises. Thus, creating a never ending cycle.

Yes it is why ..