So 32% one year ago, 20% today. China is much more sensitive to the iPhone release schedule than other markets, their drop in china has more to do with a meh on the iPhone 8 than anything else.
And Apple is one of the most profitable companies in the world no? They can't spend the money they earn. They could lose 20% and still not be able to spend what they make.
~20% in Q117, down 12% from Q116 [0]. China is their only shrinking market (at least at the granularity of data provided).
[0] https://www.apple.com/newsroom/pdfs/Q1FY17DataSummary.pdf