Comment by toomuchtodo

Don't have a percentage handy, but these resources are likely useful for your inquiry.

https://www.pewresearch.org/short-reads/2025/03/04/what-we-k...

https://www.epi.org/blog/tech-and-outsourcing-companies-cont...

https://www.uscis.gov/sites/default/files/document/reports/U...

https://www.uscis.gov/tools/reports-and-studies/h-1b-employe...

(if you email Pew Research, I've found their research team to be receptive to inquiries when they have the data but did not include it in a publication)