It’s hard to overstate the significance — and complexity — of the H-1B visa system in the U.S. It is the country’s largest guest worker visa program, and an important channel for high-skilled immigration. It allows companies to hire foreign workers for specialized jobs that can be challenging to fill. It has benefited the tech industry enormously, and other sectors, including health care, science, and finance, have also used it to fill gaps in their workforces.