iPhone sales will be one of the headlines next week when Apple reports its earnings for the fourth and final quarter of fiscal 2015.

For Apple, the iPhone is the big one, the device that generated more than half of the company’s revenue in fiscal 2014 and—thanks to the iPhone 6 and 6 Plus—an astonishing 69% in last year’s big Christmas quarter.

The arrival of the 6 and 6 Plus— the first Apple smartphones in the jumbo formats popularized by Samsung—changed the iPhone’s trajectory. Unit sales soared 46% in the Christmas quarter and kept growing, up 40% in March and 35% in June.

The consensus among Fortune‘s panel of Apple analysts—a mix of professionals and seasoned amateurs—is that iPhone sales probably grew another 24% in the September quarter.

Where the pros and the amateurs part company is in the quarter that ends Dec. 26. That’s when Apple faces what analysts have been calling the “tough compare.”

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Christmas last year wasn’t just a big quarter for Apple. It was the most profitable quarter ever recorded by any public company. And if Apple fails to match or improve on it, the short sellers will try to sweep the table.

All but two of the professional analysts we’ve heard from believe Apple will beat last year’s record 74.5 million iPhone sales. But not by much. The panel’s average estimate of about 78 million iPhones represents 4% growth, but it’s been lifted by the exuberance of a few congenitally bullish amateurs. On average, the amateurs expect iPhone unit sales to grow 9.5%. The consensus among the pros is an anemic 2%.

We’ll find out whose fourth quarter 2015 estimates were closest to the mark after the markets close on Tuesday, Oct. 27.

For the tough compare of fiscal Q1 2016, we’ll have to wait another three months.

Below: The individual analyst’s estimates—professionals in blue, independents in green. Thanks as always to Posts at Eventide’s Robert Paul Leitao for pulling together the Braeburn Group numbers.

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I’ll be monitoring Apple’s earnings report on Tuesday, Oct. 27, and you can too. The conference call with analysts begins at 5:00 p.m. ET (2:00 p.m. PT) and will be webcast live here.

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple AAPL coverage at fortune.com/ped or subscribe via his RSS feed.

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