What's the data on chain migration?

Listening to news reports about “chain migration,” I was confused. Even as someone who researches the topic, I could not tell how many people come to the United States through chain migration. If chain migration is a problem, how big or small a problem is it? I dug into the numbers to learn chain migration grows the US population by 0.25% percent, or one-quarter of one percent, annually. Here's the full article in English and Spanish. Thanks to Luis Melodelgado for the excellent Spanish translation.

Nora Haenn