Given the right circumstances human can breed at a prodigious rate but are limited by the scarcity of resources - particularly land and by rational 'fertility check'
An increase in productivity or new land then there would be a shift outwards of top curve but not bottom
Malthus only argued moral restraint could lead to higher standards of living.
- Differences in technology will only result in differences in population size, not standard of living.
- Until recently the model does well for example, in AD 1000, the technologically advanced Chinese lived at roughly the same level of subsistence as the technologically backward Europeans.
- Model does not apply at all for the last two centuries and in fact the reverse is true, the richest countries in the world have the lowest rates of population growth. Also land was replaced by capital as the key factor of production (and it is not constrained).