According to a chart posted on Apple's developer website, iOS 7 is now installed on 74 percent of all active mobile devices manufactured by the tech giant. iOS 6 still powers 22 percent of iPhones, iPads, and iPod touch models out there, while the remaining 4 percent—likely older hardware that can no longer be upgraded—are on “other” versions of the operating system.

As several publications have noted, this means that the adoption of Apple's latest operating system has jumped by nearly ten percentage points in the last month, making it the fastest-growing version of iOS ever. That’s been helped, at least in part, by the company's tradition of supporting several generations of hardware with every update.

Quick growth and fast adoption

Although Apple does not make historical information about operating system adoption available, mobile tracking firm Fiksu notes that iOS 6 was only installed on about 70 percent of devices the same number of days after its release, while iOS 5 was only able to make its way onto 65 percent of hardware.

These numbers are even more impressive once you realize that they represent percentages of an ever-growing number of overall hardware devices. Back in September, while announcing that it had sold 9 million new iPhones, Apple indicated that some 200 million users—30 percent of the total—had already updated their existing phones to iOS 7, which means that today's 74 percent translates to over half a billion devices—and that's based on an overall figure that doesn't even consider the devices that Apple has sold in the last three months.

What's missing from these statistics is a reason why users are so keen to upgrade their phones and tablets when a new version of iOS is released. Undoubtedly, a relatively simple ecosystem helps Apple make the update process easy to manage for just about any user, and the automatic update notifications built into recent versions of iOS encourage even the least sophisticated customers to keep their devices up to date.

In the specific case of iOS 7, however, the significant user interface changes introduced by the operating system may well have pushed a larger percentage of existing users to try it out just because it felt so different from its predecessors.

Good news for developers

All this adds up to an environment that is both very favorable and sometimes challenging for developers whose software must live within Apple's ecosystem, particularly at a time when the market is growing saturated with more and more apps.

On one hand, essentially all iOS users can be captured with code designed to run on the two most recent versions of the operating system, greatly simplifying the amount of work required to produce software, and allowing developers to focus on more features and better functionality.

On the other, Apple's liberal support for older hardware is a double-edged sword as far as third-party programmers are concerned. While the folks in Cupertino have enough resources to make sure that the iOS user experience is reasonably consistent even when it runs on the iPad 2 and iPhone 4, this is a much harder proposition for independent developers, which makes it challenging to create software that works well across the various generations of hardware that iOS 7 supports.

Still, compared with having to contend with a multitude of different operating systems, iOS's uniform adoption is great news for everyone involved, and a great sign that Apple's mobile ecosystem is as alive and well-curated as ever.