Shares of Micron Technology are tumbling on a Bloomberg report that Korean rival SK Hynix will build a new DRAM memory chip factory in South Korea to meet growing demand for mobile devices.

MU is down 7%, its steepest drop in 2 months. But despite today's selloff, investors who have held the stock all year still have plenty to smile about.

With a 2013 gain of 236% Micron is the 3rd-best performing stock in the S&P 500, right behind Netflix and  Best Buy:

Top S&P 500 Stocks in 2013

Ticker

Security

Last

Change

% Chg

YTD % Chg

(NFLX)

Netflix, Inc.

369.07

-5.80

-1.55%

298.61%

(BBY)

Best Buy Co., Inc.

41.25

0.03

0.07%

248.10%

(MU)

Micron Technology, Inc.

21.33

-1.60

-6.96%

236.36%