Bales of shredded cardboard, paper and packaging are arranged into towers several stories high inside Steve Young's 130,000-square-foot warehouse in Commerce, Calif.

Trucks have been unloading 600 tons of the waste paper each day for more than a week, leaving the cavernous building nearly filled to capacity.

Ordinarily, much of the scrap would have been shipped to China, where it would be mashed into pulp and recycled into cardboard boxes to package many of the goods destined for American store shelves.

But Americans aren't buying so many nicely packaged TVs, computers and toys these days. And China's economy is slowing too.

So the stacks of paper in Young's warehouse near Los Angeles are going nowhere. Prices for the material plunged as much as 75 percent in the past six weeks and probably will struggle to rebound as demand continues to fade.

But this is more than a story about unwanted paper. These piles of unwanted American trash are a window to the troubled worldwide economy, in which consumers aren't buying and the Chinese manufacturers who normally serve them are seeing a slowdown in their own breakneck growth.

"Growth in China is so tied to what's going on in the U.S.," said Peter Wang, chief executive officer of America Chung Nam Inc. of City of Industry, Calif., the largest waste paper supplier in the United States. "It's a domino effect."

Chinese manufacturers' dependence on pulp paper from the U.S. grew enormously over the past several years, as environmental degradation and logging restrictions limited their ability to find raw material to make new paper. Companies increasingly coveted recycled American paper, which was considered to be the world's finest for its strong fibers.

Last year, 11 million tons of scrap paper totaling $1.5 billion was exported to China. By contrast, only 1.1 million tons, worth $57 million, was exported to China in 1998, according to the U.S. International Trade Commission.

Last year, about 20 percent of U.S. scrap paper was sent to China. This year was on track, until the bottom fell out last month, industry experts said.

The drop in demand for waste paper is mirrored in diminished markets for other commodities previously devoured by the booming Chinese economy, including raw materials for construction and factory production.

"The developed market's weakness is hurting China and all the other emerging markets," said Donald Straszheim, a China expert at Roth Capital Partners in Newport Beach, Calif. "China has been an enormous demander of paper, copper and all iron and steel, and now that demand is way down."

The World Bank said last month that China's economic growth — 9.4 percent so far this year — might slow to 7.5 percent in 2009, which would be the lowest rate in 19 years. Chinese President Hu Jintao hinted at the depth of China's concern by warning a meeting of Communist Party leaders recently that the country risked losing its competitive edge as international demand for exports tapered, the party's official People's Daily newspaper reported.

China's slower growth combined with continued sluggish consumption in the U.S. has meant a reversal of fortunes for suppliers who had flourished along with China's boom.