Any additional workers in an area will lower wages in that area. Simple supply & demand and off course you are right that they also grow the overall pie. I do wonder though how much the added friction when changing jobs as an H1B holder creates a downward pressure. I'd bet comp in all areas with lots of H1B workers would go up if we made it much easier to change jobs while on an H1B and give a lot more time to find a new job when suddenly unemployed (1-2 years instead of weeks)