In the past two-quarters, AAPL found itself in an unfamiliar position. The world's largest company by market, has been - over the past few years - also the biggest contributor to S&P500 and tech sector earnings, and as long as AAPL's earnings were rising every quarter, this was not a problem. However, starting in Q4 of 2015, Apple found itself in the unenviable position of posting earnings which declined from a year ago. The drop was so acute in Q1 and Q2 that, AAPL alone was responsible for pushing the entire tech sector into the red on a Y/Y basis.

Which brings us to today's upcoming AAPL earnings announcement, where according to consensus, AAPL is set to report a 3rd straight quarter of annual earnings declines. According to FactSet, for the calendar third quarter (fiscal fourth quarter for Apple),the current mean EPS estimate is $1.66, compared to year-ago actual EPS of $1.96. The last time Apple reported three consecutive quarters of year-over-year earnings declines was Q1 2013 through Q3 2013 (fiscal Q2 2013 through Q4 2013 for Apple).

What may come as a surprise to readers, is that as a result of this projected decline in EPS, Apple is expected to be the largest detractor to expected earnings growth for the S&P 500 Information Technology sector for Q3 2016. The blended (combines actual results for companies that have reported and estimated results for companies yet to report) earnings growth rate for the Information Technology sector is 4.2%. Excluding Apple, the blended earnings growth rate for the sector would improve to 10.9%.

As of today, if Apple reports actual EPS equal to or below the mean EPS estimate for the quarter, it will mark the first time that Apple has been the largest detractor to earnings growth for the Information Technology sector for three consecutive quarters since Q2 2013 through Q4 2013.

Of course, if AAPL beats materially, much of this will be irrelevant; however, if AAPL misses, attention will once again turn to the driver behind Apple’s substantial contribution to the earnings decline for the Information Technology sector for Q3 2016.

Here are the key drivers behind Apple's performance this quarter:

Since Q1 2014, the iPhone product segment has accounted for about 62% of the total revenues generated by Apple on average. From Q1 2014 through Q4 2015, the iPhone product segment reported average year-over-year revenue growth of 31%. However, the segment reported a year-over-year decline in revenues in Q1 2016 (-18%) and Q2 2016 (-23%). The declines in sales are expected to continue in Q3 2016, as the iPhone product segment is projected to report a year-over-year decline in revenues of -14% for the quarter.

Another red light in this regard came from a recent Bank of America report looking at credit and debit card spending, which found none of the familiar bound in tech store spending associated with new iPhone rollouts. As BofA explained, "The latest version of the iPhone was released in September, which likely contributed to a gain in electronic store sales, following the prior four months of contraction. However, we did not see a spike in electronic store sales akin to prior releases of Apple devices. It may be a reflection of the iPhone 7 or perhaps that the trend in electronic store sales ex-iPhone is sluggish."

On the other hand, Samsung's recent problems with the Galaxy 7 whose production was terminated due to battery problems, may well have boosted demand for the iPhone.

So it all comes down to this: was the iPhone 7 a success or a flop? We will know the answer in two hours when Tim Cook unveils AAPL's Q3 numbers. Until then, here is a full breakdown of what Wall Street consensus experts.

• 4Q GAAP EPS est. $1.65 (range $1.58-$1.73)
• 4Q rev. est. $46.9b (range $45.7b-$48.3b), co. forecast $45.5b-$47.5b on July 26
• 4Q gross margin est. 37.9% (range 37.5%-38.4%), co. forecast 37.5%-38%
• 1Q rev. est. $75.3b
• 1Q gross margin est. 38.9%

UNIT BREAKDOWN

• 4Q iPhone unit est. 45.0m (10 ests. compiled by Bloomberg News)
• iPhone ASP est. $625 (5 ests.)
• 4Q iPad unit est. 9.1m (6 ests.)
• iPad ASP est. $495 (4 ests.)
• 4Q Mac unit est. 5.1m (5 ests.)
• 4Q Watch est. 2.4m (3 ests.)
• Watch ASP est. $418 (2 ests.)
• 1Q iPhone unit est. 74.9m (8 ests.)

ANALYSTS

• CLSA (buy): While investors are focused on iPhone units, it seems “far fewer” are focused on what appear to be “highly conservative” expectations for iPhone ASP. With potential for higher iPhone units and ASP, consensus estimates for FY1Q “have an upward bias,” sees FY1Q rev. forecast exceeding est.
• Goldman Sachs (buy): Sees “beat-and-raise quarter” on strength of iPhone sales due to stronger than expected carrier promotions in U.S., China and other markets, Samsung’s Note 7 problems
• Cowen (outperform): Focus on gross margin forecast, SE impact on iPhone ASP, commentary on demand from China, Apple Pay, Watch and FX
• AAPL’s ability to gain share in $700 and higher iPhone segment and generate upgrades from base of 2-year-old iPhone 6s devices should help it restore growth in iPhone product line, Bloomberg Intelligence says.