The Senate is considering eliminating the per-country quotas for those who graduate from United States universities with math, science and engineering degrees. The debate in Congress perfectly illustrates how immigration law, codified in 1965 and last revamped substantially in 1990, has lagged behind the demands of a rapidly changing economy. Unemployment in the technology industry hovers below 4 percent, far less than the national average.

In that climate, temporary visas are in such heavy demand that the total number available for the coming year — 65,000 for skilled workers and 20,000 for those with a master’s degree or higher — were snatched up in less than five days. The United States Citizenship and Immigration Services said Monday that it had received 124,000 applications in that time and had resorted to a lottery to make the final cut.

The measure being considered by lawmakers could nearly double the H-1B visas allotted yearly and possibly admit more temporary workers during periods of high demand, said several advocates who have discussed the matter with Congressional staff members and who declined to be named because the final language has not yet been released.

“If you were the human resources vice president of the United States, you would want to have a rule that says if things get busy and you need skilled people you can bring in people,” said Dan Siciliano, a law professor at Stanford. “At the same time you would want a way to bring highly skilled people in and perhaps at your choosing convert them to status that lets them stay much longer.”

A vast range of American organizations seek H-1B workers for technical jobs, from the Boston Red Sox baseball team to the chain store Nordstrom to technology companies like Google and Microsoft. Some of the largest blocs of H-1B petitions are taken by outsourcing companies, which makes them even more contentious, and critics say those firms import engineers with basic skills and pay them poorly.