The paper extends Manning's model on education and balanced growth to
include labour immigration. Each immigration unit is assumed to consis
t of one skilled worker and some unskilled members. The optimal immigr
ation policy which maximizes the per capita steady-state consumption o
f the host country is derived. We show that optimal immigration policy
can reduce the steady-state skilled labour ratio. More interesting st
ill, contrary to the widespread belief that immigration of skilled wor
kers hurts local skilled workers, it is the unskilled local workers wh
ose interests are threatened by optimal immigration policy.