Legal immigration has a comparatively small effect due to the fact that they're part of the skilled labor force and generally fill gaps in our society. The number of people actually holding H1Bs is so small that I find it hard to believe they have any major pull on the various sectors outside of the few firms that are known to be abusing the system.
Fixing the system in a humane way that also doesn't blow up the lower classes is a herculean task.
”For a typical household, a 40 percent increase in farm labor costs translates into a four percent increase in retail prices (0.30 farm share of retail prices x 0.33 farm labor share of farm revenue = 10 percent, farm labor costs rise 40 percent, and 0.4 x 10 = 3.6 percent). If farm wages rose 40 percent, and the increase were passed on fully to consumers, average spending on fresh fruits and vegetables would rise by about $21 a year (4 percent x $530 = $21).
Giving seasonal farm workers a 40 percent wage increase, on the other hand, would raise their average earnings from $11,720 for 1,000 hours of work to $16,400, lifting the average worker above the federal poverty line of $11,770 for an individual in 2015.”