N to fall. The primary cause for economic growth comes in the relative difference between Population . N and GNP . However, the growth of GNP . N can only be maintained for 30 years until Resources .
N gives out.
From year 30 to 120, GNP . N falls as does Population . N until they both collapse, at which point Resources . Trade triples GNP . N 's time of growth from 30 years to almost 90.