According to the IEEE, around 300000 (at the current limit) H1-B visas are issued in the US to foreign STEM workers each year, and they are good for 6 years. The majority are awarded to workers who come from undeveloped countries like India. They are happy just to be in the US so they gladly take tech jobs for a fraction of the pay that a US STEM graduate was reasonably expecting after graduating. There are around 1,8 million foreign H1-B workers making a total of around 5 million STEM workers in the US.
There is intense lobbying pressure on Washington to remove the limit. Apple and other corporations are pushing the myth that there is a shortage of US STEM workers. Even Obama claims that there is a shortage and wants to bring in more. BTW, there is no shortage. On the contrary, there is a surplus to the tune of 3 brand new STEM graduates in the US to every STEM job opening.
Up until Sanders and Trump brought up the issue last year, the Clintons wanted to remove the limit, so presumably the entire population of India could be issued one if they wanted. I get the impression that the Clinton is becoming evasive about the issue, but after consistently suppoerting H1B visas for 30 years I doubt her stance has changed. After 8 more years of the Clintons, STEM jobs could virtually drop to minimum wage. Trump wants to limit H1-B visas on account of the fact that these visas displace American workers with cheap labor