Saturday, October 3, 2015

Pondering Little Thought About Things

There's a saying that demographics is destiny; you may encounter it during discussions of declining western birth rates vs. the birth rates in the third world.  It's widespread problem, with declining birth rates and increasing cost of social programs throughout the US, the European Union, Japan and Russia.  That has led to wholesale importation of immigrants from the Muslim world into Europe, with the problems, some horrific, that have followed.  Ask Ayaan Hirsi Ali about some of those.  I have to believe it's possible that demographics are a major factor in Angela Merkel's rush to accept all the "refugees" coming into Germany; she needs new workers to pay for everything Germany is funding.    

But that's not where I'm going.  The other day, I had a strange thought: why do we say there was a baby boom after WWII that we consider an abnormal population surge?  The whole idea that there would be an abnormally high population bubble after WWII doesn't make sense to me.  I mean, sure there were guys who were at war, came home to their wives and had children.  I get that.  No problem.  But that's not an abnormally large rate, that's a delayed rate.   If there had been no WWII, those families would have still had those children, but probably one to five years sooner.   And don't forget, almost half a million of that generation didn't have children because they were killed in the war and those children that were never born would have made the total population larger. 

So I started looking into the birth rates and population of the US and what I found surprised me.  This the birth rate as number of children per 1000 population.  It's from the Wikipedia article on the WWII baby boom.
The red curve marks the area called the WWII baby boom.  In my heuristic (fancy word for seat of the pants) look at this, I see a crash in birth rates during the "roaring twenties" leading to an even lower rate during the Depression.  The first one seems strange.  It's my impression that during good times, people tend to feel more optimistic and have more children, while the rate tends to go down in economic down times.  So why was the birth rate declining through most of the 1920s?  If you pretend WWII hadn't happened, in order to figure out what the curve would look like if people had just kept on with their lives, my guess would be the peak from 1949 would shift to the left (earlier) and perhaps down (lower).  But what jumps out at me from this graph is how much lower that number is than the rate in 1909.  The 1909 birth rate was far higher than even the highest years of the post WWII boom.

The only thing that makes the boom look large now is the drop from a birth rate of near 22/k or so to the mid 70s birth rate of 16/k or fewer, a change most likely brought on by the introduction of "the pill" in 1960.  I think the post WWII baby boom is a demographic illusion.  To the people of the time, it seemed like it was high birth rate because it was higher than during the Great Depression while actually still being well short of their parents' or grandparents' generation.  From a more recent perspective the post war birth rate seems really high because it's compared to the much lower birth rate brought on by the introduction of the pill.  Of course, we need to add in the effects of vasectomies for contraception, as well. 

Stated another way, the only reason we have a bubble of baby boomers heading toward retirement is that the children who could have been in succeeding generations were either prevented or, later, aborted.  Just looking at numbers.  I believe the US birth rate is currently still below replacement levels (20 on this chart).  Like Europe, we're attempting to get around that by immigration.  Like Europe, I expect trouble coming because of that. 


  1. Fascinating post, and makes perfect sense. Thanks!

    This is why I check in on your blog regularly. You make me think, and that's always a good thing. :-)

  2. Most of those who say "Demographics is Destiny" pick and choose facts to fit their political views - and oversimplify the impact of the changes.
    For example, while the Caucasian portion of the population in the US is shrinking, many commenters don't point out that it is moving as well; the Northeast is losing numbers due to both moving and low birth rates while religious areas of the West and South are growing due to both factors.
    To give another example: Hispanics are the biggest growing part of our population, yet like most immigrant populations of the past after the first generation voting patterns and party allegiances splinter as they identify more as American than with their ancestor's culture.
    Past experience shows we can't predict what demographics will effect in a decade, so why do people trumpet generational forecasts as set in stone? The one certainty in life is change, both from what we have now and from what we expect to happen - For example, we still don't have a flying car!

  3. Take the "S-curve" out of the WWII area, and you have a nice, declining curve across the entire graph. The big question is why. It looks to me as though WWI took the desire to procreate out of western civilization.

    Running a lowpass filter on it and it's clear as a bell (the right side of the bell ;-)

  4. Maletrope - I think that most potent contraceptive found is prosperity. It just seems that as soon as people get any economic breathing room over bare survival, they stop having kids.

    Birth rates in poor countries are higher than wealthy countries.

  5. Navy91 - thanks for your kind words, and pardon my late answer.

  6. I agree - there are other studies that show that higher prosperity leads to fewer kids. Some of them show that the biggest driver of the number of kids a family (and therefore a society) has is the education level of the mother - more education = fewer kids; personally I think it is stretching to make that direct a connection, but I see their point.
    China is in particular trouble because they pushed the One Child Policy and now with advancing incomes the rate is dropping from there instead of from the higher level it would have been without the policy.
    In the US, I believe that second generation Hispanics have fewer kids but I don't have a source of study to back that up.