… is from page 188 of the late, great economic historian Stanley Lebergott’s indispensable 1984 volume, The Americans: An Economic Record  (footnote deleted):
Mass migration to the United States shaped the U.S. economy in a variety of ways. Most vital was the continuous instability it brought. Local monopolies of labor and enterprise were broken up by immigrants. Techniques of production were upset by the succession of new views and conflicting attitudes. Where business had a monopoly, where labor controlled entry to an occupation, where engineers promulgated a traditional method of production – there resources were unlikely to be used with high efficiency. But the free market in ideas, the persistent competition of novelty, kept surfacing ever more efficient production techniques, then got them adopted. It is no mere chance that the greater stability of production methods in the plantation South contrasted with continuous change, industrialization, and economic advance of the North. For the flow of immigrants to the North and West was never ending; that to the South was minuscule.