CHANGCHUN - Wang Chang, a pig farm manager, reduced his breeding stock as he predicted falling pork prices. In fact, prices plummeted faster than he expected.

Pork prices are at a four-year low in the world's biggest pork market.

Wang said a 10-kg pig that sold for 780 yuan ($122.5) in 2016, now sells for just 300 yuan.

Wang's company has eight pig farms in Northeast China's Jilin province, and saw output of 50,000 pigs last year.

"I reduced the breeding stock by 400 pigs at the most in each farm this year, but still suffered losses of 3 million yuan in the first quarter," said the deputy manager of the Jilin Hongzhui Pig Breeding Co Ltd.

In 2016, pork sales brought the company 20 million yuan in profit, while in 2017, profit shrank to 5 million yuan.

Jilin is one of the most important granaries in China, and a major pig breeding ground. Wang Yaqin, a farmer in Lishu county, has raised pigs for 22 years, but felt confused about the price tumble, as it has fallen every day, especially since this year.

"Two years ago, I could earn 600 yuan from raising a pig, but now I would lose 300 yuan by raising one," she said.

According to pork price monitoring by the Chinese Ministry of Agriculture and Rural Affairs, at 500 county-level farm produce markets, the average pork price in the third week of April amounted to 10.87 yuan per kg, down 1.3 percent from a week ago, and 31.7 percent lower than the same period of last year.

Liang Qi, an agriculture product price expert, said pork was China's staple meat and its price subject to a boom-and-bust cycle depending on supply and demand.

"However,the prolonged cycle of price fall suggests asymmetric information of the supply and the demand sides, as they are separated by links in the production chain including slaughtering, cold chain logistics and meat processing," she said.

Liang called for a nationwide big-data information service system for early warning of pork prices in order to help guide farmers in production.