Difference in factor avail ability
Difference in costs
Difference in wants
Difference in currency system
Encouragement for balanced growth
Absence of tariff
Restrictions on the movement of goods
Existence of anti-dumping policy
Become indeterminate
Become continuously favourable
Continuously become unfavourable
Become constant
ex =em=1
ex + em >l
ex + em
ex + em=1
Robert Solow
J. E. Meade
Paul Rom
T. W. Swan