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- Tim Cook said iPhone sales grew in China, despite external research showing a decline.
- The discrepancy may be due to different methods of calculating revenue used by Apple and analysts.
- China accounted for 18% of Apple's sales, making it a critical market for the tech giant.
Apple told investors on Friday that iPhone sales grew in China in the first three months of the year, a surprise to analysts who had dissected industry reports in recent months that appeared to show the opposite.
The difference may stem from how Apple and external analysts calculate revenue.
"We still saw growth on iPhone in some markets, including mainland China," CEO Tim Cook said on Apple's Friday earnings call.