Legal immigration is governed by categories: family sponsorship, employment, humanitarian admission, and a diversity lottery. Annual caps and per-country limits produce backlogs measured in years and sometimes decades.
The current category structure dates largely to 1965 legislation that replaced national-origin quotas with a system weighted toward family reunification. Overall numeric limits have changed little since 1990 while the economy and population have grown.
Per-country caps mean applicants from large countries wait far longer than applicants from small ones with identical qualifications. Employment-based backlogs for nationals of some countries extend beyond a working lifetime.
Temporary visa programs cover specialty occupations, seasonal agriculture, intracompany transfers, and students. Employer sponsorship ties status to a job, which affects worker bargaining position and mobility.