From David McKenzie at the World Bank finance blog, the per capita income gain from 6 kinds of interventions:
The paper is here. Quibble with the numbers as much as you like, these are massive differences.
After learning that Intel’s co-founder was a refugee resettled in the US by IRC, I have begun to wonder: if 0.005% of refugees and immigrants transform the US economy, is the annual gain from immigration to current citizens of the US equally large?
See also Ryan Pevnick on the ethics of immigration policy.