The annual number of babies born in Japan slipped below 1 million in 2016 for the first time since records began, with the estimated figure for the year coming in at 981,000, according to government figures released Thursday.

The number dropped an estimated 25,000 from the previous year, according to a survey by the Health, Labor and Welfare Ministry. The annual figure had previously remained above 1 million every year since records began in 1899.

The ministry said the main factor behind the figure is a decline in the population of women in their 20s and 30s, and the trend will continue unless the age composition of Japan's graying population changes.