One of the aspects of the immigration system that a new Senate proposal seeks to reform is the shortage of visas for workers in the science and technology fields. The proposal would increase the number of temporary visas, as well as green cards for more immigrants to become permanent citizens. The bill contains provisions to increase and decrease the number of visas available in accordance with demand.
See "Skilled Science Workers at Focus of Second Senate Proposal on Immigration", Julia Preston, The New York Times, January 28, 2013