Japan's birth count tells a story of three distinct eras: the pre-war plateau around 1.5–2.3M, the explosive post-war baby boom peaking at 2.70M in 1949, a second echo boom in the early 1970s, and then relentless decline since 1973 reaching a historic low of 727K in 2023.
Grouping the 125 years into five eras reveals how different demographic regimes shaped Japan's population trajectory.
TFR fell from 4.54 in 1947 to 1.20 in 2023. The replacement threshold of 2.07 was crossed in 1975 and has never recovered. The 2005 trough of 1.26 prompted major policy responses but only minor rebounds.
The crude birth rate collapsed from 34.3 in 1947 to just 6.0 in 2023 — a drop of 82.5%. This reflects both declining fertility and Japan's rapidly ageing population base.
The ratio of male-to-female births per 100 girls has remained remarkably stable between 103–107 for 125 years. The 1906 anomaly (108.7) stands out as a notable outlier. No long-term trend exists — biology dominates.
Male births consistently exceed female births by ~5% throughout all 125 years. Both sexes follow the identical macro trend, confirming the sex ratio is independent of demographic conditions.
Japan's post-war baby boom saw 3 consecutive years of ~2.68–2.70M births with TFR above 4.3. The pre-boom (1943–45) had already elevated births due to wartime pronatalism, but demobilization in 1945–46 supercharged fertility. This cohort later drove the 1971–74 echo boom.
In 1966 — the Hinoeuma (Fire Horse) year occurring every 60 years in the Chinese zodiac — births plummeted to 1,360,974, a 25.5% drop from 1965. Superstition held that women born in Hinoeuma bring misfortune to their husbands. Births rebounded sharply to 1.94M in 1967.
Every decade since the 1970s has seen a lower average than its predecessor. The 2020s are on pace to average under 800K — a level not seen since records began in 1899.
Most years see negative growth after 1973. The largest single-year drops: 1966 (-25.5%, Hinoeuma), 1950→1951 and 1949→1950 as the baby boom began normalizing. Recent years show consistent -2% to -5% annual declines.
Top years cluster in 1947–1950 (post-war boom). Bottom years are all post-2018 — meaning the last 6 years are the 6 lowest on record.
The 125-year arc can be divided into 5 clear demographic phases, each with its own driver and pace of change.
The strong positive correlation (r ≈ 0.97) between TFR and total birth count confirms that fertility rate — not population size — is the primary driver of birth decline. Every 0.1 drop in TFR corresponds to roughly 75,000–100,000 fewer annual births.
The absolute gender gap (male minus female births) peaked at ~83,000 during the 1949 baby boom and has shrunk to just ~18,000 in 2023 — purely because total births have collapsed, not because the sex ratio changed.
Based on the 2010–2023 linear decline trend, Japan could see births below 600K by ~2028 and potentially below 500K by ~2034. However, the rate of decline has been accelerating recently, making the actual threshold date potentially earlier.
Japan's TFR has been below replacement (2.07) since 1975. It crossed the 1.5 "very low fertility" threshold around 1993 and has spent the last 30 years in this critical zone. The 2023 value of 1.20 is far below even the lowest sustainable fertility projections.