Fertility and Superstition

Look at the impact of superstition on the fertility rate of Japan in 1966...the year of the fire horse (Hinoeuma)

'The Hinoeuma year in Chinese astrology comes once every 60 years. In Japan, women born in the Hinoeuma year are believed to be headstrong and deadly to men. This superstition was spread widely among the population and people avoided having children in the Hinoeuma year.'

Source

[Thanks to Shino for this information]