Restrictionists have argued that specific characteristics of immigrants relative to natives harm immigrant-receiving countries. The broad types of arguments are listed below:

• Skills mismatch: The skills of immigrants simply aren’t suited to the needs of a modern society, which is where they are interested in immigrating to.
• IQ deficit: Immigrants have systematically lower IQs than natives, and this affects a range of socio-economic indicators.
• Dysfunctional immigrant culture

Note that there is a slightly different version of the argument that focuses on the increase in societal heterogenity that results from immigration, and how this may lead to social capital decline and/or other second-order harms. The argument here is not so much that immigrant characteristics themselves are responsible for the problem, but rather, the differences between immigrants and natives, even if not morally salient, are responsible for trouble.