The skills, efficiency, and broader institutional knowledge (how individual contractors, developers, and municipalities work) developed and relayed throughout a mulitilingual industry would literally never be replaced, given how our current training and recruitment mechanisms function. Never ever.
Reposted from Ed Z
20% of the US construction workforce is made up of undocumented immigrants. The US construction workforce increases at an avg rate of about 3%/year. If we were to lose those undocumented workers, it would take about 6-7 years to replace them, if ever. Could set back construction almost a decade.

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