This is my take.
I believe the Borgs numbers. They may stretch the truth but I don't think they are cooking the books.
There are NO middle class families joining. All growth is 1. Born in. 2. Foreign language. 3. Destitute. The median age of a dub is way older than the median age of the U.S. this will catch up with them soon. Within 5 years US growth will be zero or negative.