Each month, an official in the US Department of State looks at a number of statistics. Specifically, he looks at how many immigrant visas and Green Cards have been issued during the fiscal year so far to applicants from each country, and in each category. This will tell him how many are left in each category. He divides this by the number of months left in the year to find out how many should be approved in the next month.
He also looks at how many people may no longer qualify, are not interested any more, or for other reasons not pursue immigration, and how processing delays at USCIS would affect the process, and makes an educated guess of how many petitions should become now become eligible to hit the target quota.
Next, he looks at how many petitions have been filed, and when they have been filed. He then essentially counts off the oldest ones until he has enough to approximately hit the number of people who should get a GC or immigrant visa this month. This determines the priority date in the category.
All this has to be done separately for each country.
If his guess is wrong, or if USCIS suddenly develops or clears a processing backlog of Adjustment of Status applications, it sometimes happens that far more or fewer immigrant visas or Green Cards are issued during a month than predicted. In that situation, he needs to adjust the current priority date for the next month to correct for this. This is why sometimes the priority dates retrogress. If such a situation causes the whole annual quota to be exceeded, he has to mark the category as "Unavailable" (in the visa bulletin, you will see the letter U to indicate this situation).
Usually, none. You are most likely already a US citizen.
The exception to this rule is if your parents were in the USA as diplomats. In that case, you would be chargeable to your country of citizenship, or if you are not a citizen of any country, to your last country of residence (presumably, if you are already residing in the USA, that would mean the previous place of residence).
There have been some rumors that a special immigration category exists for children of diplomats born in the US. I have no further information as to the truth of this rumor, and have doubts about the truth of them. Any such category should be listed in the INA, but I did not find anything there.
You should be asking this question even though it may seem obvious if you are from a large country that is likely to send many immigrants to the USA. These countries are currently India, Mexico, the Philippines. You should also ask this question if you are from China, since this country teeters on the brink of being such a high-immigration country.
You should also be asking this question if you participate in the Green Card lottery, regardless of where you are from.
Your country of chargeability is usually determined by your place of birth. If your place of birth has changed countries, what counts is the country your place of birth is in today. For instance, if you were born in the now-Polish cities of Gdansk or Wroclaw before World War II, when they were the German cities of Danzig or Breslau, respectively, you would fall under the Polish quota. Similar situations arise in the former Soviet Union, as well as many other countries.
There are certain situations when you are allowed to be counted in a country different from your country of birth. This is know as alternate chargeability (or sometimes alternate nativity). The most common situation is if you are married, and your spouse is chargeable to a different country. In this case, you are free to choose your spouse's country instead of your own (some conditions apply).
I looked up the quota backlog on the Dept. of State site, and the priority date is some time in 1992. But the USCIS Web site says that they are processing applications from 1998. What gives?
Thanks to Mike for suggesting this question.
These two dates really have nothing much to do with each other. The priority date is a delay that is written into the law. It determines when you are eligible to file an application for an immigrant visa or for adjustment of status.
The USCIS date tells you when they are actually processing a petition (the form I-130).
So let's say that you filed a petition on March 7, 1997. In that case, you would have a priority date of 1997. Because USCIS is processing I-130s from 1998, you would probably already have an approved I-130 in your hands. But you would still be waiting quite a few years. Just put the approved I-130 into a bank vault or some other safe place. As soon as the current priority date has advanced past March 7, 1997, you are eligible to actually use the I-130 - until that day, it is just a meaningless piece of paper.
There actually are two separate quota systems in place. The first quota system limits the number of people who can apply in each category, regardless of their country of birth. The second quota limits the number of people who can immigrate from any one country (this goes by the place you were born, not your nationality!). This per-country quota says that no country can send more than 7% of the total worldwide immigration (this translates to 25,620). Unfortunately, this system puts large countries at a disadvantage; the quota is the same for India and China with a billion people each as for Nauru, with approximately 10,000 people.
If many people from one country want to immigrate to the USA. the total number of immigrants may reach the per-country quota, and the number of people admitted in all immigration quotas will be reduced for this country.
Dependent areas, such as Hong Kong, are counted separately and have a lower annual quota.
I see in the visa bulletin that my category has a backlog of four years. That means I can get a Green Card four years from now, right?
Unfortunately, no. It means that people who applied four years ago are now eligible. If in the meantime more than four year's worth of people applied (which is likely in most family-based categories), then your wait will be longer. The actual time you have to wait is unpredictable and most likely much longer than the visa bulletin suggests.
For an example, look at the Family 1st category. At the time of this writing (Visa Bulletin for July 2003), the current priority date for most countries is December 15, 1999 - almost four years backlog. In June 2000, the current priority date in this category was December 15, 1998. In other words, in this category it took three years for the current priority date to just move by one year! If this rate persists (which by no means is certain), somebody who applies today would be eligible for a Green Card in about ten years rather than the three 1/2 years that the visa bulletin suggests.
My priority date is current, but the consulate is refusing to issue an immigrant visa anyway, saying that this is because there is no quota number left. How can this happen?
This occurs if the priority date was set too generously, and enough people already received their Green Cards to fill the full annual quota. In this case, it would be actually illegal for Department of State to issue an immigrant visa beyond the quota. Remember that the legally binding factor is the total annual quota; the priority date is merely a mechanism to implement it.
If this happens, you should see the visa category change to "Unavailable" in the next month. A new quota will become available in October. There is unfortunately no guarantee that your priority date will still be current in October. In fact, it is likely that the priority date will be set a bit earlier to avoid repeating this situation.
This depends on your situation. If you are outside the USA, the consulate will notify you when your priority date is current. The actual date that matters is the date the immigrant visa is issued (usually, the same date the interview takes place). An immigrant visa can only be issued if during that month, your priority date is current.
If you are inside the USA and apply for adjustment of status, the priority date is important at two points in the process. First, you can only file an I-485 if your priority date is current. Second, your I-485 can only be approved if your priority date is current. Sometimes, when priority dates retrogress, you may have been able to file the I-485 one month, and when USCIS is ready to approve your I-485, the priority date is no longer current. In that case, they will put your case back on the shelf and keep it pending. You should carefully monitor your case and be sure to call USCIS to make sure they remember to pull it off the shelf again when your priority date is current again.