Today, Apple CEO Tim Cook started off an earnings call with analysts by talking about everyone's favorite subject: foreign currency markets! Yes, we know you care more about Apple's plan to vary the hue of your iPhone's backlight. But Cook took pains to explain that the dollar was to blame for Apple not making more dollars.

In effect, Apple seems eager to convey that, because the dollar has been so strong, US goods (including the iPhone) are expensive for consumers overseas. At the same time, the volatility of foreign currencies make it so that citizens in those countries have less money to spend.

It's understandable that Apple feels the need to explain itself. Today, in spite of reporting the largest quarterly profit in history—its own or anyone else’s—the company also predicted its first overall drop in sales since 2003. The company also reported the slowest growth ever in iPhone sales. By the relative standards of Apple’s universe, that could be enough to get shareholders feeling skittish.

Hence Cook's decision to play a little defense. “Two-thirds of Apple’s revenue is now generated outside of the US, so foreign currency fluctuations have a very meaningful impact on our results,” Cook said.

According to Apple's slide deck, revenue would have been $5 billion higher at a constant exchange rate—a fluctuation that, as Cook pointed out, could amount to the entire respectable revenue of a Fortune 500 company. At least, a Fortune 500 company that isn't Apple.