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A pedestrian walks by an Apple Store on January 24, 2012 in San Francisco, Calif. Apple shares have soared for much of the year, but now they are being hit by something called 'profit taking.' - 

Jeremy Hobson: Isaac Newton's Law of Gravity appears to be hitting Apple's stock. The company's shares dropped about 4 percent yesterday. Its five-day losing streak has wiped out some $60 billion in Apple's market value. But analysts aren't calling what's happening gravity. They're using a different term: to explain the drop: 'profit taking.'

Marketplace's John Dimsdale explains.

John Dimsdale: 'Profit taking' is when investors who got in early on a rising stock want to cash out. That fits Apple's stock performance, which is up 43 percent this year, fueled by exploding sales of iPhones and iPads.

James Cox is a Duke University securities professor.

James Cox: For those who believe in active management and timing when you buy and when you sell stocks, rather than just going in for the long haul, now 's a good time to take advantage of that terrific runup that Apple's had over the last many many months. Step back, see where the market is going to hit a low and then buy the stock again.

Some analysts are predicting Apple's string of electronic hits is unsustainable. But Cox explains that the term 'profit taking' is used when the stock's downturn is expected to be temporary. In the long-run, he says, Apple is still a good investment.

In Washington, I'm John Dimsdale for Marketplace.