I know we just went through the labor market where we discussed the factors affecting labor supply. The main factors were the birth rates, baby boomer generation, woman entering the labor force, and retirement age. I didn't go into a lot of detail about immigration. This is primary because illegal immigrant do not affect the labor supply in the United States. They are taking jobs American do not want to work. This is evident by the United Farm Workers campaign, "Take Our Jobs". They have opened up 700,000 jobs current occupied by immigrants. Only 16 people have applied for these positions (including Stephen Colbert). Here is nice piece by Ezra Klein.
So how can more immigration increase the wages of low skilled American workers?