A piece in todays online OpinionJournal by Prof. Arthur C. Brooks highlights the phenomenon of different reproductive rates of liberals and conservatives. According to Brooks, there is a significant "fertility gap" between liberals and conservatives. As you might guess, conservatives are more prolific. As Brooks states: "According to the 2004 General Social Survey, if you picked 100 unrelated politically liberal adults at random, you would find that they had, between them, 147 children. If you picked 100 conservatives, you would find 208 kids. That's a "fertility gap" of 41%. " The full story can be found here (but I think you must be a WSJ subscriber - sorry):
These reproductive rates seem rather high for both groups, as even the liberals are more than effective at replacing their populations, something which is not true in most European countries. The CIA World Fact Book states that the fertility rate for the U.S. is 2.09 children born per woman. Thus, assuming roughly half of the sample are women, you would expect only about 100 children for the average group. By comparison, the fertility rate in the U.K. is 1.66 children per woman, well below the rate needed to replace the population.
(The CIA World Fact Book can be found here:
https://www.cia.gov/cia/publications/factbook/geos/us.html Of course, if you don't trust the CIA, you may be a liberal! Just kidding, of course.)
The point that Brooks is making here is that through the magic of compounding, if we assume the conservatives continue their population growth rate, and if we assume that like produces like (i.e., conservative parents generate conservative progeny), there is a cloud on the horizon for the liberal-leaning folks in the U.S. Of course, it may be possible for a liberal to "evolve" from a conservative parent, or for a liberal parent to produce a conservative offspring (remember Alex Keaton? That dates me a bit.) These forms of "mutation" could frustrate Brooks' prediction.
Moreover, fertility rates do not tell the whole story of population. There is also the matter of immigration affecting the voting public. Herein lies a significant point: liberal immigration policies could affect the population balance among native-born citizens, affecting the politics to come. I will have to rely on my colleague Professor Clark to address that empirical question of which direction immigrants lean in the U.S., but this feature does potentially highlight the future interests of political parties in addressing immigration policy (or not, as the case may be).
I don't know if Brooks is correct, but I do know that getting on the wrong side of the magic of compound interest is not the place to be. You'll have to decide for yourself which side you want to be on.