12. Recall the discussion in “Letting the Data Speak” regarding the Chinese yuan. Why did the Chinese authorities keep the yuan undervalued until the end of 2016? At the beginning of 2014, $1 was valued roughly at 6.05 yuan, while by the end of 2016, $1 was valued at 6.95 yuan, since then it has stabilized at $1 = 6.35 yuan by early March 2018. What factor may have caused the strengthening of the Chinese currency since early 2017?