But as Webster pointed out, the big question -- how much revenue those downloads have produced -- is murkier.
The 27 million can't be used to deduce the number of paying customers because the Office for iPad apps can be downloaded free of charge for viewing documents, spreadsheets and presentations. (Unlike Word, Excel or PowerPoint, the free OneNote app offers full functionality.) To activate advanced features -- including document creation and editing -- users must have a valid subscription to an Office 365 rent-not-buy plan.
Microsoft has given little insight into the success of Office 365, and none into what part Office for iPad may have played. Microsoft's most regularly-touted number has been the active subscriptions to Office 365 Home, the pricier of two consumer-grade plans.
Word for iPad has been downloaded the most of any of the suite's iOS apps, according to lists kept by trackers like AppAnnie.
In a conference call with Wall Street analysts several weeks ago, Microsoft said it had 4.4 million Office 365 Home subscribers on the rolls, an increase of 26% in three months. The company has not, however, updated that number since April; if it had, it might give some clues about Office for iPad's impact on subscriptions.
The 27 million downloads surely led to some new subscriptions. But how many?
"Remember, some people already have access to Office 365," said IDC's Webster, referring to consumers who had previously plunked down $100 for a year's subscription or employees at firms that have shifted from on-premises perpetual licenses to Office 365. Both user categories would have rights to Office for iPad, and thus reason to download one, more than one, or all the suite's apps.
On the other hand, if 10% of those who downloaded an average of two apps subsequently became new subscribers to Office 365 Home, Microsoft would have added 1.35 million subscribers. Five percent? That's 675,000 additions to the list. Similarly, if one assumed an average of three app downloads per user, Office 365 collected between 450,000 (5% of the total) and 900,000 new customers (10%).
Revenue? At $100 per user per year, and using the above assumptions, Microsoft would have put between $45 million and $135 million on the books annually. Or not.
That's because another unknown part of the revenue equation is what percentage of the Office for iPad-fueled new subscriptions went through Apple's App Store -- the Office apps offer in-app purchasing of Office 365 Home -- and thus what cut Cupertino received and what Redmond was forced to concede.
For example, if 900,000 new subscriptions were processed through the App Store, Apple would have kept $27 million of the $90 million total, leaving Microsoft with $63 million for the year.
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