Articles about chain migration have three common characteristics:

1) They are presented as thoughtful, in-depth discussion of the topic;

2) They are quick to arrive at conclusions and hammer then in repeatedly;

and

3) They are extremely sparse in details.

You can read a hundred such articles without understanding what percent of legal migration is due to chain migration, what exactly is chain migration, and how it works. But when you are done reading this article, you will be such an expert that all your friends will turn to you for advice and succor on the subject.

Let's look at total legal immigration in 2015, courtesy of the Center for Immigration Studies:

The data is a little confusing because of how chain migration is defined. Chain migration, which is defined as immigrants bringing in related immigrants, is a subset of family migration, which includes native-born American citizens bringing in immigrant spouses.

For purposes of this discussion, however, I am going to treat all family migration as chain migration, as it covers people being brought into the country who are not vetted for professional capabilities. You may think that bringing in spouses of native born US Citizens shouldn't be considered part of chain migration, but in cases where first generation Americans (such as grown up anchor babies) sponsor spouses, it should be considered part of chain migration.

Another interesting fact to notice about the chart above is that "sons" and "daughters" refer to adult children while "children" refer to, well, underage children. The F-2 category above refers to both kinds.

What we can glean from the facts above is that family based migration accounted for 825,000 legal immigrants in 2015. That's a very large number, and the vast majority of all immigrants admitted in 2015.

The next largest category is refugees, which was 150,000. This number has shrunk radically under Trump, but it is up to each president to unilaterally decide how many to admit every year, so a future president Kamala Harris or Cory Booker could admit 200,000, 400,000 or even more.

Another category is the random lottery, which brought in 75,000 people, again with no vetting for job skills or employability. And finally the last category is employment or merit based, for those who have needed job skills. That number was less than 150,000 in 2015. As you can see, nearly 90% of legal immigrants were not vetted for job skills.

Some key facts from the CIS report:

• Over the last 35 years, chain migration has greatly exceeded new immigration. Out of 33 million immigrants admitted to the United States from 1981 to 2016, about 20 million were chain migration immigrants (61 percent).

• Judging from preliminary administrative data, approximately 1,125,000 legal immigrants were approved for admission in 2016, which is about 7 percent higher than 2015, and one of the highest numbers in the last decade.

• The largest categories of chain migration are spouses and parents of naturalized U.S. citizens because admissions in these categories are unlimited by law.

• According to the most complete contemporary academic studies on chain migration, in recent years each new immigrant sponsored an average of 3.45 additional immigrants. In the early 1980s, the chain migration multiplier was 2.59, or more than 30 percent lower.

• Of the top immigrant-sending countries, Mexico has the highest rate of chain migration. In the most recent five-year cohort of immigrants studied (1996-2000), each new Mexican immigrant sponsored 6.38 additional legal immigrants.

What Trump has proposed is to eliminate the lottery system (now around 50,000 slots) and to limit chain migration to spouses and underage children, no parents, no brothers or sisters, and no adult children.

However, that would still allow spouses and underage children. If we assume that 75% of the F-2 category are spouses and underage children, and you add that to spouses of US Citizens who are given visas, that means about 400,000 family based migrants would still be coming into the country every year, without regard to merit, even under Trump's limited chain migration plan. That number would still dwarf the number of employment based visas given out on merit every year. It would still allow hundreds of thousands of new citizens into the country who have not been vetted for job skills.

It would be a vast improvement over what we have now, where some 85% of people entering the country are not vetted for job skills, but is not an ideal long term immigration policy.

Ed Straker is the senior writer at Newsmachete.com.