The demographic transition began in the developed nations around 1850:<p><a href="https://en.wikipedia.org/wiki/Demographic_transition" rel="nofollow">https://en.wikipedia.org/wiki/Demographic_transition</a><p>My great-grandmother (mom's mom's mom) had 16 children. My mom had 4. My mom's 4 children are done having children, and my mom currently has 3 grandchildren.<p>Life expectancy at birth has increased 6 hours every day since 1850. That trend has been surprisingly steady, despite a few World Wars and depressions. 6 hours every day. That works out to 2.5 years per decade, and over 16 decades, that works out to 40 years. Thus the average lifespan has moved from around the age of 40 to around the age of 80.<p>Occasionally I read an article with a sensational headline such as "A new baby boom!" because fertility has moved from some small number to some slightly larger, but still small, number. Or other times the sensational headline goes the other way: "Baby Bust! Is your retirement fund in peril?"<p>Against all such minor variations in the medium-term trend, it is worth remembering that the the long-term trend has been down. In 16 decades, the only really serious, world-wide break from the trend was 1945 to 1953, and that was clearly a response to the war.<p>The most interesting break from the trend was the so-called English-speaking Baby Boom, which occurred in Australia, New Zealand, Canada, Great Britain and the USA. It started in the late 1930s, then stopped due to the war, then started again in 1945, and the birth rate climbed until 1958, and it remained high till the mid 1960s.<p>Outside of that one major deviation, the trend has been down for a very long time.<p>Meanwhile, the Earth's overall population has had its biggest run ever. The last time the human population of the Earth fell is thought to have been the Great Plague of 1347 to 1350, but the boom since 1800 has no precedent. There were 1 billion humans alive in 1800, 2 billion in 1900, 3 billion in 1950, 4 billion in the 1970s.<p>There are roughly 7 billion people alive today.<p>Try to keep all that in mind when you read about variations in the birth trend.