What are the most over and under rated demographic trends today?

[mieastwick]

Another underrated one:

Liberal whites do not really have many kids anymore and tend not to marry until very late in life, while conservative whites are still having a lot of babies.

I think the only High Birth Rate demographic is Foreign Born-Hispanic Women currently. I don't think Non-Hispanic White Women Republicans are having any more or any less babies than Non-Hispanic White Democrat Women.

Your thoughts are wrong; Republican non-Hispanic White women certainly are having more babies than non-Hispanic White Democratic ones. The marriage gap was the best predictor of how each state voted in 2012. Look at Vermont's total fertility rate. Now look at North Dakota's, or even Tennessee's.