So, how many a year is "actually let some people through the legit way?" How many is SOME? Why do you make stuff up?
Here is 50k we just give away as Lottery, to offset the big legal immeigarte countries, Mexico, Brazil, United Kingdom and China.
http://blog.usa.gov/post/10847287614/how-to-enroll-in-the-u-s-visa-lottery
There are many ways to legally immigrate to the United States, but only one of them depends completely on luck: the congressional mandated visa lottery, which offers 50,000 green cards to people from certain countries.
The Diversity Immigrant Visa Program is open to countries with low rates of immigration to the United States, such as Malaysia, Belarus, and Algeria. In order to diversify the immigrant population of the U.S., participation is limited to countries with less than 50,000 new immigrants to the United States per year.
Citizens from countries with already high rates of immigration such as Mexico, Brazil, United Kingdom and China are not eligible to apply. You can learn more about which countries qualify from the State Department’s
Diversity Visa page.