The debate over how to value the yuan is at the heart of the two-year struggle by the country’s policymakers to slow down China’s overheating economy. One response was the decision by the People’s Bank of China to increase the one-year interest rate from 5.31% to 5.58%– its first rate hike in over nine years – in an effort to curb fixed-investment growth, staunch increasing prices, and offset a worrying decline in savings.