September 2017
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Day September 26, 2017

Face Time

Since the iPhone launched 10 years ago, 1,253,000,000 units have been sold.[1] Given that they don’t last forever, we can assume that only the most recent units sold are still in use. If we measure just the units sold in the last 3 years, the total is about 663 million. Rounding down, we can say that there are perhaps 650 million iPhones in use.

Repeating the exercise for the iPad but extending time in use to 4.5 years, gives a population or install base of about 240 million.

That’s a total base of 890 iOS million units, well below the 1 billion total “active devices” Apple reported in January 2016. The difference can be filled by Apple Watch, Apple TV, iPods and Macs.

Apple also reports that the iPhones get unlocked 80 times per day. That figure was also reported in early 2016. We don’t have a figure for the iPad but I’m going to take a guess of 15 unlocks per day on average. Feel free to argue about these figures in the comments below.

Now, if each of these iOS devices would be unlocked using a 4-digit PIN, the time to bring them into use would be about 2 seconds. Expanding to a 6-digit PIN would probably increase that to perhaps 2.5 seconds (accounting also for failures due to input errors.)

Moving to 6 digits, although more secure, would add friction and hence time to the unlock process. This reminds me of the story of Steve Jobs arguing that decreasing boot times for the Macintosh would save lives. I wondered what would be the savings in time for speeding up the unlock process.

It turns out that, based on the installed base numbers, moving to the more secure 6-digit code would add 2.8 billion hours to the total time to unlock the world’s iPhones and iPads. That’s 321,000 years of waiting added for every year of use.

Fortunately we got Touch ID to replace PIN entry and the time to unlock the iPhone/iPad has decreased to perhaps 1 second, saving 5.6 billion hours of unlock time vs. 4-digit PIN.

Now we have the prospect of Face ID which promises to be faster still. Of course, it won’t be available on all iOS devices for some time, but if it that base of 890 million iOS devices were to migrate to Face ID and if it took a mere 0.5 seconds to unlock, Face ID would save nearly 8.5 billion hours of time that otherwise would be spent typing unlock codes.[2]

That’s almost a million years.

That’s 12,500 lifetimes.

I’m glad to see Steve’s ideas continue to motivate Apple engineers.



  1. This includes the current quarter that ends in 4 days []
  2. Given this methodology one wonders how much time is spent using, rather than just unlocking, iOS devices. I’ll leave that as an exercise to the reader. []