What determines immigration's impact?

"Can history shed light on the modern debate about immigration's labor market impact in high wage economies? This paper examines the relationship between migration and capital flows in the age of mass migration before 1914, the so-called first global century. It then assesses the effects of immigration on wages and employment with and without international capital mobility in first global century and today, that is, the second global century. The paper then explores the links between these economic relationships and immigration policy. It concludes with an explanation for the apparent difference in immigration's impact in the two global centuries, and thus on policy"--National Bureau of Economic Research web site.