The future is female (and old & lonely)

My last post looked at declining birth rate and increased numbers of children being born outside of marriage…

Today, I will dive deeper into the implications of the declining birth rate into what it possibly portends for the future population of the United States. Note that I am not a demographer and I expect any number of demographers who do this for a living have created far more sophisticated population models and I suspect nothing I report here is truly “new”. However my goal is to demonstrate some of the implications that may not be obvious or known to us regular folks who don’t do this for a living.

My starting point is the estimated 2022 population by individual age and sex in the US (e.g. how many 3 year old girls, 4 year old girls, etc.). To this data I add the current birth rates by age group that was used in the previous post. Finally, I use death rates by age group and sex. With these three pieces of data, I can “simulate” the changes in population (ignoring immigration¹).

Namely:

1. The population of 0-1 year olds in a given year is simply the number of births from child-bearing age women in the population of the previous year, then split by sex. I divide births 51.1% male, 48.9% female which was the estimated split in 2022.

2. The estimated population for any other age/sex is the population from the previous year of 1 year younger folks of the same sex, minus the number expected to die based on age and sex.

Using this relatively simple arithmetic, I can project the population by age & sex into the future (again, based only on current US population, ignoring future immigration). The year 2100 was a nice round number, so my spreadsheet spit out numbers that far. The following general trends can be seen.

Native born population decline is imminent

Here is the projection of total births and total deaths based on current birth/death rates by age and the current population:

As can be seen above, the deaths (red) start exceeding the births (green) among the current population as early as next year. From there, the gap widens quickly. Deaths>Births → declining population.

By end of century, population (excluding immigration) declines ~44% and its old & lonely

Using the method specified above, from the current US population, we would expect still living people + their living descendants to represent a population decline of 44%, going from ~333 million in 2022 to ~186 million in 2100. Moreover, the age of the population projects to be significantly different:

Notice above the youngest and oldest major age groups. While we have almost 7M more people alive in 2100 that are older than 75, the number of people under 25 craters from ~104M to ~41M 😱. Roughly speaking, with ~31M >75 year olds, and ~41M <25 year olds, that basically means the average grandparent has a total of 1 grandchild (lonely). On the economic front, the implications for government retirement systems that require young workers’ tax dollars for funding are obvious as well.

The future is female

As the population is increasingly made up of older folks, and as death rates diverge between men & women as they age, we can also expect the population to be more heavily female in the future:

We see that the current population is 50.4% female, while the projection for 2100 is 51.6% female. This may not seem like a large change, but looking at the raw numbers illustrates (at least to me) that is a bigger deal than 1st thought. In 2022, there are 2.8M more women than men (out of a population of ~333M), while in 2100 there projects to be ~5.9M more women than men (out of a population of only ~186M). I suspect that will be noticable. What impact it has, 🤷‍♂️

Limitations

First, I will say that many of a fool has done the practice of taking a current tend, assuming nothing will change, projecting it out to the future and making some conclusions. When done in a pessimistic way (as in this post), we typically associate this method with Thomas Malthus (or in recent times, Paul Ehrlich of “The Population Bomb” fame). Therefore, I am 100% open to the possibility that (nearly) everything I say above will turn out to be wrong. But I don’t think so. Again, because I am ignoring immigration, there are really only two levers to pull in this projection, birth rates and death rates. Let’s look at each and make a best guess of which direction I’m likely wrong and what it means to the major trends above:

• Birth rates: I used the most recent birth rates for my analysis. If anything, I feel like this is being conservative as rates have actually been declining. In order for the above picture to be better, we need a reversal of recent (worldwide)trends². If I were a betting man, I’d be more likely to wager that birth rates in future decades decline even further than present rates. Further decreases in birth rates would lead to:

  • Population decline would be more significant

  • The population would be more skewed towards the elderly

  • The population would be more skewed towards women

• Death rates: Again, I used most recent rates. In general (although not the last few years), life expectancies have increase and death rates have decreased in the past decades. Therefore, using the current rates can be viewed as too pessimistic going forward. Fair enough. But if death rates continue to drop in the future, it will be primarily in the older (post childbearing years). Death rates among the young do not have much room to drop further in the US. Therefore, if death rates do decline in the future, the result would be:

  • Population decline would not be quite as significant

  • The population would be more skewed towards the elderly

  • The population would be more skewed towards women

So, again, although I am reluctant to project 80+ years into the future assuming a current trend continues, there is a decent chance my projections are too optimistic.

1. Obviously immigration will have a significant impact on the population of the US. Perhaps I will come back to trying to include this as well. What I will say, however, is that

• Immigration is difficult to predict

• There is not a factory out there producing an infinite number of immigrants (birth rates are falling in nearly every developed nation and many underdeveloped nations as well)

• If the idea is that the US will sustain or grow its population based on immigration, there will be plenty other countries in the same position and in possible competition for those immigrants, e.g. Europe, Japan, South Korea, Australia, etc

2. Potential game-changer in this area would some type of technical advancement in reproduction that enabled an increase in birth rate in new ways. Scientific discovery that allowed women’s reproductive age range to increase dramatically? Cloning? “Factory” babies? Yeah, I’m creeped out by the last two, but just putting out there things that would change the formula.