Why are an estimated 85 percent of the North Koreans who manage to make their way to freedom in South Korea women?

And why do nearly all come by way of China, rather than across the heavily guarded DMZ, and have sad stories of sexual abuse to tell?

The backward North Korean economy produces very little that the world wants. But Big Brother China, however, is hungry for the two things Pyongyang does have in relative abundance: coal and women. The coal keeps the fires burning in energy-poor China. The women help to meet the shortage of brides in China's male-dominated society.

China's one-child policy has devastated the female population. Over the past three-and-a-half decades that the policy has been in place, tens of millions of girls have disappeared from the population. They were killed in utero by sex-selection abortions, at birth by female infanticide, or after birth by simple neglect.

Sex-selection abortion is the biggest offender. Almost ten million such abortions were carried out between the years 2000 and 2014. That works out to 1800 unborn girls eliminated every day, 640,000 eliminated each year, and six and half million each decade.

Coal keeps the fires burning in energy-poor China. The women help to meet the shortage of brides in China's male-dominated society.

This targeting of unborn baby girls has so skewed the sex ratio at birth that there are now at least 115 boys born for every 100 girls.

The result is that women of marriageable age are in short supply. There are now an estimated 33 million men in China who cannot find brides--at least inside of China. And so they look abroad.

The State Department's 2013 "Trafficking in Persons Report" acknowledged the connection, stating that "the Chinese government's birth control policy and a cultural preference for sons, create a skewed sex-ration of 118 boys to 100 girls in China, which served as a key source of demand for the trafficking of foreign women as brides for Chinese men and for forced prostitution."

One place that Chinese men look for brides is the other side of the Yalu River, for in North Korea there are lots of hungry young women longing for a better life. The population of Kim Jong Un's socialist paradise subsists in near famine conditions, with two in five North Koreans undernourished and more than two-thirds on food aid.

The latest United Nations report, published in March 2017, paints a grim picture: Out of a population of 24 million, "an estimated 18 million people are dependent on Government food rations while 10.5 million people are believed to be undernourished. A lack of access to basic services including water and sanitation, as well as a weak health infrastructure further threaten the well-being of the population, particularly young children and pregnant and breastfeeding women.

Even members of Kim's highly touted "one-million man army" are starving; witness the sick and malnourished defector who recently crawled across the DMZ to freedom.

As a result of this widespread and continuing food shortage, starving North Korea peasants are often happy to sell a teenaged daughter--whom they would have trouble feeding in any event--to agents who claim that they are recruiting workers for Chinese companies. "Your daughter will be given a job in a factory or restaurant," they promise the parents. "She will finally have enough to eat."

Older women are also lured across the border on the same promise.

But these "hiring agents" are actually sex traffickers, and what awaits the North Korean girls and women in China is not a real job but either forced marriage or out-and-out sexual slavery. Young girls, especially if they are virgins, are sold to the highest bidder as brides. Older women are generally sold to brothels where they are kept under lock and key and forced to work as prostitutes.

It is no wonder that many of them take flight at the first opportunity, paying "snakeheads"--illegal guides--to lead them safely across China's southern border to Vietnam, Laos, and Thailand. From there they can easily travel to South Korea and freedom.

“Historically, the largest influence in female migration from North Korea to China has been sex trafficking and marriages,” said Sokeel Park, the Seoul-based director of research and strategy for Liberty in North Korea, an organization that helps rescue North Korean refugees hiding in China.

Having found their way to freedom, few of these woman will go on record saying that they were forced into prostitution or sold as wives in China. But nearly all, as vulnerable women in a country with a superabundance of often predatory males, were sexually abused in some way.