Visa Numbers

Every country has a set amount of immigrant visas (green cards) that they get per year. (The DHS year starts on Oct 01). Thus a visa number must be available at the time when you get your green card. Naturally countries with huge populations (like India and China for Employment based, and Mexico for Family based) use up their visa numbers quickly and thus the people born from those countries have to wait longer. The USCIS gives visa numbers based on "Priority dates." Priority dates is the on which the USCIS receipts your case, ie the I-140 for Employment based and I-130 for Family based applications. This ensures that the first come application gets served first.

Immigration Laws have also devised categories. The Employment based categories are as follows:

Employment Based (EB) 1: No labor certification required. File only I-140 and I-485
Available for
L-1A Managers
Outstanding Professor or Researcher
Extraordinary Ability Aliens

EB-2 Labor Certification required
Available for
Advanced Degree Holders (at least a Master’s Degree)
Exceptional Ability

EB-3 Labor Certification required
Members of a Profession (at least Bachelor’s Degree)

EB-4 Religious Workers

EB-5 Investor (No labor certification or I-140 petitions. Instead file I-526)
Must invest $1 million in cities Or
$500,000 in areas of “Targeted Employment” and
Employ 10 full-time U.S. workers

The Family Based numbers are as follows:

NO WAIT: US Citizens’ spouse, parents and children under 21 have no wait time, and can come over or adjust status immediately

First Preference: Over 21 unmarried children of citizens

Second Preference-2A: Spouses, minor children (less than 21) of permanent residents (green card holders)

Second Preference 2B: Unmarried sons and daughters over 21 of permanent residents (green card holders)

Third Preference: Married sons and daughters of US Citizens

Fourth Preference: Brothers and sisters of adult citizens

Thus the wait time depends on your priority date, Preference Category and of course your country of birth.

For Employment based visas you can use either your country of birth or your spouse's country of birth.

The visa bulletin, published by the Department of State every month gives the dates/Preference category/country. To see the visa bulletin, click here:

http://travel.state.gov/visa/frvi/bulletin/bulletin_1360.html