Based on my earlier research at Generating a Marin County population projection, I knew that Marin County was "old" in terms of demographics. This is because, since 2000, Marin County's population has grown much slower than either California or the US (left-hand graph below). Its population growth is better aligned with Italy (right-hand graph below).
Additionally, Marin County's life expectancy is way longer than the US. It is even longer than the one for Italy or Japan. See more on the subject here Is Marin County a Blue Zone?
Slow population growth combined with long life expectancy makes for old-looking age pyramid graphs.
Marin's age pyramid is way older than California's or the US
You can see that on the pyramid graphs below. Marin's pyramid already looked like an inverted urn by 2000 and even more so by 2021, indicating more older individuals and fewer younger ones. By comparison, both California and the US have maintained a relatively resilient proportion of youngsters.
The main takeaways from the pyramid graphs above include:
- Between 1970 and 2021, Marin has aged a lot faster than either California or the US;
- In 1970, Marin's pyramid is nearly as old as California or the US in 2021;
- In 1985, Marin's pyramid is already way older than California or the US in 2021;
- In 2021, Marin's pyramid is a lot older than either California or the US.
Marin's age pyramid structure is very similar to Italy and Japan
You can observe that by looking at the age pyramid graphs below.
And, Marin County is similar to Italy and Japan.
Marin's wave graph is way older than California's or the US
A wave graph is informative as it is the equivalent of consecutively aggregating yearly pyramid graphs from 1970 to 2021 or 51 pyramid graphs! And, the wave graph gives you information on the yearly population change of each age tranche over time.
The wave graphs below confirm that Marin is way older than California or the US.
Main takeaways from the above wave graphs:
- Notice how Marin's population has grown a lot less than either California or the US. You can see that Marin's wave graph has remained relatively flat since 1970;
- On a relative basis, over time Marin's tranche of 65 years old and above has become so much thicker than for California or the US;
- On a relative basis, over time Marin's tranches of 24 years old and younger have narrowed; Meanwhile, it is not so much the case for California and the US.
Marin's wave graph is very similar to Italy and Japan
Main takeaways from the above graph:
- The wave graphs for Marin County and Italy have nearly identical shapes with very similar relative proportions of the different age tranches;
- Japan's wave graph is a bit different than the other two. Notice how rapidly the tranche of the 65 + has thickened;
- Notice that all three wave graphs indicate that the respective populations have already peaked, and are currently already declining.
Long-term population prospect
These three regions with such rapidly aging pyramids and wave graphs are positioned to potentially experience a dramatic decline in population over the next two or three centuries. This is a prospect I modeled recently, including projecting Marin County's population and benchmarking it with a similar projection for Italy.
A prospective long-term precipitous decline in population is not limited to Marin County and Italy, it is a common possibility throughout much of the developed World. For more on the subject:
The NYT article published the following graph (describing the prospective path of the World's population) that pretty much said it all.