This paper examines the dynamic implications of border control policies and
internal enforcement measures for the pattern of illegal immigration and t
he sectoral allocation of clandestine foreign workers. It is argued that ef
forts to control illegal immigration in sectors where they traditionally fi
nd employment may trigger the formation of networks supporting clandestine
foreign workers in new locations and occupations where the probability of d
etection is relatively lower. The end result may be an increase in the over
all stock of illegal immigrants residing in the economy. JEL classification
: F22, R23.