How Apple's Stock Performs After New iPhone Announcements

When Apple unveils its new iPhone tomorrow - we're expecting an iPhone 5S and a cut-price iPhone 5C - do not expect Apple's stock to behave predictably.

Usually, investors bid up stocks in advance of major announcements, and then sell them after the news is out. "Buy the rumor, sell the news," as the saying goes. But Apple's stock doesn't behave that way, depending on the time period you're looking at.

Here are a couple of charts illustrating AAPL's progress before and after new iPhone releases.

First, Fortune's Philip Elmer-DeWitt, using data from Deutsche Bank, shows that Apple's stock rose in the long term after four iPhone releases and only fell after two:

But CNN Money sees a different post-iPhone pattern. In the month after the announcement, AAPL dropped five out of six times:

Johnny Evans at ComputerWorld notes that consumer interest in the new iPhone drops off a cliff almost immediately after the new model is revealed:

This time around, AAPL has lifted in advance of the news, although that may be as much to do with the expectation that Apple has signed a major new Chinese wireless carrier to sell its phones: