SEOUL, June 9 -- The economy that decades of Western sanctions were designed to strangle is, by the best measures anyone has, in the middle of its strongest run in more than a decade. North Korea has posted the fastest growth of Kim Jong Un's rule, a quiet boom that the architects of the pressure campaign against it did not plan for and have struggled to explain.

The numbers come from the Bank of Korea in Seoul, which produces the standard outside estimate of an economy that publishes almost nothing about itself. It put North Korea's real output up 3.7 percent in 2024, to around $26.6 billion, the largest expansion in years. Manufacturing rose 7 percent, the most in a quarter of a century, and mining climbed 8.8 percent, its best showing...