This one chart shows why it's so important for Apple to revive iPhone sales (AAPL)

Since its launch ten years ago, the iPhone has sold over a billion devices, triggering Apple's rise to the most valuable company in the world.

But a recent trend has started to worry some Apple investors: declining iPhone sales. In fact, in its fiscal 2016, iPhone sales grew at the slowest pace since the iPhone was introduced in 2007. That's particularly concerning for Apple, given how the iPhone is the single most important product for the company. As seen in this chart by Statista, roughly 60% of Apple's revenue came from iPhone sales in 2016, after generating a whopping 69% of total revenue in the first two quarters of 2015.

And with all of its hardware products seeing sales declines last quarter, it's no surprise that some investors are questioning if Apple has "lost its mojo."

Statista

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