https://www.glassdoor.com/research/h1b-workers/
"The bottom line: Across the 10 cities and roughly 100 jobs we examined, salaries for foreign H1B workers are about 2.8 percent higher than comparable U.S. salaries on Glassdoor. While it may be true that an influx of H1B workers in the 1990s hurt computer science wages, there’s no evidence in the data on Glassdoor that H1B workers today represent a source of “cheap” labor paid any lower than comparable U.S. workers."
Comparing H1B and U.S. Wages
"To compare salaries for H1B and U.S. workers, we used a sample of 58,025 salary offers listed on H1B visa applications for workers in 10 large U.S. cities in fiscal year 2016 from the U.S. Department of Labor.
As a comparison group of U.S. workers, we pulled a sample of 101,728 full-time U.S. salaries reported on Glassdoor for a similar time period, in the same 10 cities. We then grouped both samples into similar types of jobs, and looked at roughly 100 jobs for which there was significant data (at least 100 salaries in both H1B and Glassdoor salary samples).
We ran a simple regression of annual salary on controls for city and job title, along with a binary indicator equal to 0 if it was a U.S. salary on Glassdoor and 1 for a H1B visa salary. The estimated coefficient on the H1B visa indicator tells us the average difference in pay between U.S. and foreign workers after accounting for differences in the city and job they worked in.
The table below shows our results. The coefficient on the “H1B Visa = 1” variable shows that foreign H1B salaries are 2.8 percent higher on average than comparable U.S. salaries — a statistically significant difference. Thus, there’s no evidence that H1B workers are paid any lower than comparable U.S. salaries – and, in fact, earn slightly more – once we carefully compare workers in the same jobs, in the same cities, during the same time period in fiscal year 2016."