It is well-known that lack of support for single mothers was a major source of why many children in Korea were given up for adoption, but to this extent?  From Hosu Kim’s Birth Mothers and Transnational Adoption Practice in South Korea:

Single mothers constitute the great majority of all birth mothers involved in transnational adoption from South Korea. More than 120,000 children, or two out of three adoptees, were, or are, children of single mothers. Single mothers are referred to as mihonmo, which literally means “not-yet-married mothers.” Due to the high rate at which children of mihonmo are sent away for adoption, the term has become synonymous with birth mother. The conflation of these two categories in common parlance, however, misrepresents the population of South Korean birth mothers as comprised entirely of single mothers. 2 But more importantly, it introduces the expectation that a single mother should relinquish her baby to adoption. To examine how single mothers are rendered into birth mothers, I analyze a critical historical juncture during which single motherhood increasingly accounted for the children placed into transnational adoption. This period occurred between the 1980s and the mid-2000s, when children born of single mothers accounted for 80 to 90 % of all transnationally adopted children.

The fact that the same word is used for both single mothers and adoption birth mothers is also stunning to learn.