The People’s Bank of China said it acted because the yuan has been rising even when market forces say it should be falling. Worried Chinese have been moving money out of the country, putting downward pressure on the yuan. Yet the yuan has remained up anyway because of its link to the dollar, which has been rising. An overvalued yuan has hurt Chinese exporters by making their products more expensive overseas. In July, Chinese exports plunged 8.3% year over year. China’s economy already needed help. The economy is expected to grow less than 7% this year, its slowest rate since 1990, and could decelerate even more next year. The stock market has been in a freefall since June.