This week the US Supreme Court ruled against the Defense of Marriage Act, ignoring the fundamental good to society of promoting marriages among those able to bear children and the underlying nature of sexuality itself. Most conservatives believe that children come from sex. Conversely, many liberals believe children come from failed contraception. These different opinions account for the liberal-conservative divide on abortion, contraception, and the definition of marriage.
Ideas matter, and these two different ideas have serious reproductive consequences. In fact, just by looking at a map, we can see which states have decided that sex should be a normatively sterile act.
First, the United States is a large and diverse place. The difference between fertility in Utah and fertility in Vermont is larger than the difference between the highest and the lowest fertility countries in Europe.
Second, notice where the low fertility states are located. Except for states along the US-Mexican border, the map almost perfectly aligns with a red-and-blue state map depicting political orientation. That’s right: conservative states have higher fertility and liberal states have lower fertility, much lower.
The border states do have higher fertility. For instance, California, which was the subject of this week’s Supreme Court ruling on Proposition 8, has a fertility rate of 1.98 children per woman. But, if we looked at Californian fertility without Latinas, California’s fertility is only 1.68, putting it well below the national average. In fact, without Latinas, California’s fertility rate is lower than Denmark’s.
Third, only 7 states in the country have above-replacement fertility, and on average, US fertility is below replacement. Replacement fertility for a developed country is 2.1 children per woman (one kid to replace the mom, one to replace the dad, and 0.1 kids for mortality), but American fertility currently sits at 1.9 children per woman–below 2.1.
Now, population controllers are still worried about the United States. Like Support US Population Stabilization, SUSPS, many population controllers still say things like: "The United States, at a population of over 291 million, is the world's third most populous country, after China and India, and has the highest population growth rate of all industrialized countries. Fertility, or birhts per woman, contributes to our population growth and must be addressed in order to acheive population stabilization."
Even though the US population is still growing, it won’t be for long. The population is still growing because — as my demography professor in college taught me — it takes a long time to stop a large ship. That is, the United States population is still growing because we have so many people who are of childbearing age; our population is still growing because our parents had above-replacement fertility. This lag between a population reaching below-replacement fertility and actually shrinking is called population momentum.
Don’t let population controllers fool you, the US population will shrink unless current trends change.
Turning the United States around towards a sustainable population will take a long time, much like trying to reverse a large ship. But before we can reverse the demographic trends, ideological trends need to change as well. The myth of overpopulation needs to be debunked and current sexual ideology needs to change.
 Last, Jonathan. What to Expect When No One’s Expecting: America’s Coming Demographic Disaster. New York: Encounter Books, 2013.
 Myers, Dowell. “California’s Diminishing Resource: Children.” Lucile Packard Foundation for Children’s Health. January, 2013.
 Mather, Mark. "Fact Sheet: The Decline in US Fertility." Population Reference Bureau. July 2012.
 Martin, Joyce et al. “National Vital Statistics Reports.” National Vital Statistics Reports 60.1 (2012).