Apple's stock just went into the red for the year (AAPL)

Apple stock closed at $168.49 on Friday, sliding more than 3%.
Apple is now down for the year. On the last day of trading in 2017, December 29, it closed at $169.23. 
Apple stock has had a wild year of ups and downs. It gained through the first nine months of the year — spurred by tax cuts, share buybacks, and rising iPhone prices. 
But it has slumped over the past two months. It's lost 27% since October 3, when it closed at $232.07, wiping out its gains for the year. 
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