China’s foreign exchange reserves declined by about $100 billion in January, falling to their lowest level since May 2012, as the country’s central bank sold U.S. dollars to cushion a rapid descent in the yuan’s value, as well as to stem capital outflows. Foreign cash reserves dropped to $3.23 trillion, the People’s Bank of China reportedly said in a statement released Sunday.

Economists surveyed by Bloomberg forecast a deeper cut in the world’s largest cash hoard, expecting it shrink to $3.21 trillion. China’s foreign exchange reserves fell by more than $500 billion during 2015 — the first ever annual drop — as the Chinese government battled a stock market rout, slowing factory production and falling exports last year. Beijing is burning through its cash reserves in efforts to prop up the yuan and to spur economic growth through stimulus measures.

Zhou Hao, an economist at Commerzbank, told the Financial Times that although the extent of the reduction in forex reserves was “not surprising”, it highlighted the policy challenge the government faced.

The rapid pace of declines in yuan’s value has prompted investors to trade their yuan-denominated assets for safe haven currencies like U.S. dollars and Japanese yen.

“Domestic private investors and global currency traders see a one-way bet against the currency. This has resulted in large-scale private capital outflows since early 2015 as expectations mount that the PBOC will eventually be forced to capitulate once its reserves are sufficiently depleted,” Rajiv Biswas, Asia-Pacific chief economist at IHS Global Insight in Singapore, told Bloomberg.

Meanwhile, financial policymakers have stepped up efforts to control the forex outflows, intervening in the Hong Kong market last month after the yuan’s exchange rate offshore sank to a record 2.9 percent lower than the rate in the mainland currency markets.

The Chinese currency has declined 1.24 percent against the U.S. dollar so far this year.