== A theory of decline

One of the periodically recurring tropes in anime is humanity being in
decline; not through a loud apocalypse or for any visible reason, but
people are just quietly diminishing. This season's *Jinrui wa Suitai
Shimashita* puts this in the series premise (the title of the show means
'Humanity Has Declined') but there are plenty of others, such as [[*Sora
no Woto* SoraNoWoto]] and the classic *Yokohama Kaidashi Kikou*. In the
version of the trope that I'm thinking of, the cause of the decline
is never stated (and the decline itself is often just a background
detail, not the main focus of the show). One of the things that this
generates is a lot of speculation about why humanity is in decline in
any particular show. What catastrophe do the creators imagine having hit
us?

As it happens, I have a theory on this. Japanese creators are almost
uniquely placed to vividly feel one particular quiet catastrophe in
real life: ~~a low birth rate~~. The Japanese total fertility rate
is one of the lowest in the world, well under the replacement rate
necessary to just hold the population level constant (see eg [[Wikipedia
http://en.wikipedia.org/wiki/Demographics_of_Japan]]). The effects of
this decline are apparently visible all over Japan, especially in less
attractive areas with lower populations. The whole issue is considered
a serious problem (especially when combined with an aging population),
with various government attempts to encourage children, discussion in
the press, and so on. Extrapolating Japan's very real issue with a low
birth rate into a future setting is a natural thing to do.

(As you'd expect, I believe that one of the most visible signs is fewer
and fewer schools with fewer and fewer pupils. This has cropped up as a
plot point in contemporary shows; for example, I remember the climax of
the GTO live action series taking place at a now-shut-down rural school
that one of the characters had attended.)

A really low birth rate is a great fit for the typical anime decline of
humanity. It's slow but devastating, it's quiet, and there's nothing
really to fight or to make a fuss about. There's no singular event
that's causing the problem, just a whole collection of small individual
decisions. Life goes on, the world shrinks (because there are fewer and
fewer people in it), and so on.

(And with fewer people in the world you start to progressively
lose technology that you no longer have the manpower to run the
infrastructure for. It takes a lot of people all through a supply chain
to run a modern chip fab, for example, especially once you include
things like the transportation infrastructure, the water supply, and so
on.)