Apple (AAPL)  has long been criticized for relying too heavily on its iPhone for revenue, but just how dependent is Apple on the ground-breaking device? 

If you combine Apple's iPhone revenues from the first two quarters of 2017 ($54.4 billion for Q1 and $33.2 billion for Q2) with Wall Street's estimates for iPhones sales in the second half of 2017 ($25.5 billion for Q3 and $29.4 billion for Q4), it adds to $142.5 billion of Apple's total expected revenue of $225.5 billion for the 2017 fiscal year.

In other words, the iPhone is estimated to account for 63.1% of Apple's revenue this year. 

But that's not unusual. Since the iPhone first came out in 2007, the iPhone has made up a little over half of Apple's total revenue, according to a calculation from Jackdaw Research chief analyst Jan Dawson. Since 2011, that has risen even higher, hitting a high of 66.3% in the 2015 financial year. 

The iPhone revolutionized the phone market, but some analysts and investors are wondering how much longer the company can rely on a device that was the brainchild of former CEO Steve Jobs, who died in October 2011. Consumers and others have been waiting for Apple CEO Tim Cook to release another game-changer since he took over -- but hopefully they weren't holding their breath. 

Earlier this month, former Apple creative director Hugh Dubberly told TheStreet that he was disappointed in Apple's lack of innovation since Cook took over in 2011. "Steve is gone and so the creative direction is gone," he said. 

Investors will be paying close attention to Apple's iPhone sales when Apple reports its fiscal third quarter earnings after Tuesday's market close. Apple sold 50.8 million iPhones last quarter, which was a drop from the 51.2 million units sold in the previous quarter. For the typically slower third quarter, analysts are expecting Apple to report 40.8 million devices sold.  

The third quarter, which encompasses the months of April through June, is historically a soft quarter for iPhones sales due to Apple's tradition of releasing a new model each September. That means the excitement over the latest iPhone has died down and consumers that need a new iPhone could be holding out for the latest edition, due out in a few months. 

Apple's latest iPhone models, the 7 and 7 Plus, came out in September of 2016. According to some reports, the 2017 iPhone models' launch date is being pushed back to October or November due to supply constraints.

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