Infants are seen at a postpartum care center in Seoul, April 24. Newsis

More babies in Korea are born to parents who are not legally married, and the ratio of births occurring outside of marriage hit a record high of 4.7 percent in 2023, data showed Wednesday.

The data Statistics Korea released comes as the number of marriages in Korea plummeted 40 percent from 2013 to 2023, leading to a decrease in the country's overall birthrate.

The agency said a total of 230,000 babies were born last year, down 7.7 percent from 2022.

The 2023 figure also marked the lowest since the agency began compiling relevant data in 1970.

On the other hand, 10,900 infants, or 4.7 percent of the 230,000 newborns, were extramarital births.

The rate is the highest to date, steadily increasing from 2.1 percent in 2013 to 2.5 percent in 2020, 2.9 percent in 2021 and 3.9 percent in 2022.

"The increase in births outside of marriage is mainly attributable to the high cost of marriage and changing social norms," Statistics Korea said.

It pointed out that a total of 193,673 marriages were reported in 2023, slightly higher than the 191,690 marriages reported a year earlier but 40 percent lower than 322,807 in 2013.

Last year, more than 30 percent of those in their 20s or 30s cited "lack of money" was a reason for not getting married.

The average age of women giving birth in 2023 reached a record high of 33.6, up by 0.1 from a year earlier. The average age of fathers was 36.1.

Under these circumstances, the number of births dropped for the eighth consecutive year in 2023 to 230,000, down 47.3 percent from 436,455 tallied in 2013.

The country's fertility rate, which had already been the world's lowest, fell to 0.72 in 2023.

The fertility rate refers to the average number of children a woman is expected to have over her lifetime.

It is far below the rate of 2.1 per woman needed for Korea to maintain its population steady at 51 million.

In the meantime, the number of births bounced back for the first time in more than eight years in the second quarter of 2024, according to Statistics Korea.

It said a total of 56,838 babies were born in the April to June period. This was up 1.2 percent from a year earlier and marked the first increase since the fourth quarter of 2015 when the number went up 0.6 percent.

The total fertility rate was at 0.71 in the second quarter, remaining unchanged from a year earlier.