This paper analyzes the welfare effects of immigration and its subsequ
ent effect on ethnic diversity in a model featuring human capital spil
lovers which depend on the degree of ethnic heterogeneity, variation r
ates of time preference across individuals and endogenous levels of im
migration and assimilation. In the model, an increase in ethnic divers
ity reduces the spillovers effect for the majority. Nonetheless, immig
ration can be welfare improving for the majority ethnic group even if
it increases the degree of diversity as long as it raises the average
human capital level and/or growth rate by increasing the proportion of
people with low rates of time preference. However, if an economy is t
oo homogenous, it will not be able to attract immigrants. Finally, if
the level of immigration is not too high, then immigration also raises
the net benefits to assimilation which leads to a more homogenous eco
nomy.