The rupiah appreciated by 14.4% against the US dollar on an annual average basis in 2010, and by the end of the year it had reached Rp8,991:US$1, more than regaining the ground lost since late 2008, when the currency plunged as international investors fled risky emerging markets. Interest from international investors in carry trades (whereby speculators borrow in countries where interest rates are low, such as the US and Japan, to purchase assets in countries with higher rates, such as Indonesia) has been an important factor in the rupiah's appreciation. Healthy domestic economic growth has been another factor encouraging foreign investment in Indonesian assets. Substantial capital inflows are expected in 2011, when Indonesia's GDP growth performance and interest rates will compare favourably with those of Western economies, but BI will continue to intervene to prevent the currency from appreciating too sharply. The rupiah is forecast to strengthen by 2.7% on average in 2011, before weakening slowly in 2012-15. The currency will remain vulnerable to sudden swings in sentiment.