Data: The trade volume publicly disclosed by the customs of China and North Korea is only $2.3 billion on the surface, but the "China-North Korea Friendship Oil Pipeline" delivers 500,000 tons of crude oil to North Korea every year, which has never been recorded in the customs accounts for decades. This is essentially a covert lifeline.

China gives away hundreds of thousands of tons of grain, vegetables, meat, as well as Chinese industrial products and construction projects at rock-bottom prices to North Korea for free every year. Combined with unofficial trade, the American think tank Stimson Center once estimated that China's annual aid to North Korea amounts to nearly $20 billion. Without China's lifeline, North Korea would not survive a year.

If this money were used to subsidize the Chinese people, it could fully cover the annual pension gap.

This is the "brotherly friendship forged in blood," except that the blood being shed is that of the Chinese people.