BEIJING, Jan 23 (Reuters) -
* China's exports of alumina in December fell by 37.9 percent from the previous month to 177,430 tonnes, according to data released by the General Administration of Customs on Wednesday.
* The figure was up more than 3,700 percent from December 2017 after a year that saw China ship unusually high volumes of the substance used to make aluminium.
* Full-year exports were 1.46 million tonnes in 2018, customs said, more than 25 times greater than the 2017 total.
* Chinese producers cashed in on a favourable price arbitrage to international markets in 2018, as an outage at Norsk Hydro's Alunorte plant, a strike at Alcoa's operations in Western Australia and U.S. sanctions on Rusal led to a global supply squeeze.
* International alumina prices fell by around 30 percent over the fourth quarter, reducing the incentive for Chinese producers to export.
* China, traditionally a net importer of alumina, imported 50,000 tonnes of alumina in December and 510,000 tonnes over the full year, customs said. (Reporting by Tom Daly; editing by Christian Schmollinger)