Japan's birth rate dropped precipitiously in 1966, only to recover completely in 1967.
This is apparently because 1966 was the "Year of the Fire Horse" - that is, in the 60-year zodiacal cycle you get by crossing the twelve zodiac animals with the five traditional elements (fire, water, earth, wood, metal), 1966 was in the Horse Year of the Fire cycle - and women actively avoided having children in that year because children born in that year were said to have poor prospects for marriage.
Is there some sort of mythological story explaining why it's so bad to be born in the Year of the Fire Horse?