The technology analyst Benedict Evans recently tweeted the chart below, which is based on data from Enders Analysis.

Evans notes that the estimated number of smartphones in use is about to pass the number of PCs in use — probably in the first half of 2014.

The number of smartphones sold per year blew past PCs sold per year a couple of years ago. But the installed base of PCs is more than 1.5 billion, and they generally last a lot longer than smartphones. Tablets, meanwhile, which will probably start outselling PCs next year, are still a distant third in terms of installed base.

In a follow-up tweet, Evans notes that the PC installed base is estimated using 5-year trailing PC sales, while the smartphone and tablet installed base uses 2-year trailing sales.

Based on a still-functioning home-office PC from 2005 that I still use occasionally, as well as an only recently deceased iPhone 3GS, both usage lives may be conservative.

Here’s Evans’ tweet.

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