參考：http://www.hooyou.com/familybased/index.html

就是說不同親屬種類，有不同的配額限製，透過每個月的排期表就可以估計自己的申請大概多少年可以被批準。
Each Preference is given a numerical quota per year to limit the number of immigrants admitted into the United States

Each Preference is given a numerical quota per year to limit the number of immigrants admitted into the United States. - See more at: http://www.hooyou.com/familybased/index.html#sthash.lpv8xiDa.dpuf