Why did waste paper prices swing so violently in China?

Why did waste paper prices swing so violently in China?
The 2017 spike was a supply shock, not a demand story. Environmental policy sharply restricted imported fiber, and imported waste paper fell to roughly 34 percent of raw material, down from a much larger share, leaving domestic collection to fill the gap. Containerboard and corrugated grades depend on waste paper for 80 to 90 percent of feedstock, so any tightening transmits straight into paper prices. The result was a rollercoaster: collection prices climbed from around 0.4 yuan per kilogram toward 2 yuan within a year, then whipsawed after the National Day holiday. Packing station owners who held stock captured windfall gains, while small collectors squeezed between rising purchase costs and thin resale margins captured almost none of the upside.