Are there any rough estimates of the total number of person-hours that have been spent on writing FLOSS software? (paid and volunteer)

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In 2000, David Wheeler made a serious attempt to enumerate the total amount of code in a representative distro (Red Hat 6.2), finding that it contained around 17 million source lines of code. Using the Constructive Cost Model, he estimated that that represented about four and a half thousand person-years of development time.

He repeated the exercise a year later for Red Hat 7.1, finding 30 million lines of code, representing eight thousand person-years.

That work stimulated other analyses using the same logic, and the tools Wheeler developed, which are documented here. The most recent of them counted the code in Debian Wheezy, in 2012, finding around 420 million lines of code, and a total equivalent development cost of USD19bn. He uses a typical annual developer wage of USD72,533, which I calculate to be 263,000 person-years. This article also breaks down the figures for some individual projects, including SaMBa, apache web server, and PHP.

There is no central repository of free software, so I doubt a definitive number can ever be reached, but there are some attempts to reach a lower bound.

  • “Measuring programming progress by lines of code is like measuring aircraft building progress by weight.” I've spent days analyzing a problem and in the end solved it by writing a single line of code and I've spent minutes copy- and pasting thousands of lines.
    – Philipp
    Apr 21, 2016 at 14:33
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    @Philipp I think that's a very fair point. If you have a better way to count the time the world has spent writing free software, now would be a good time to mention it!
    – MadHatter
    Apr 21, 2016 at 14:46
  • Why would red hat have so much less code than debian? Apr 30, 2016 at 22:14
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    @RenéG I'm not sure that it does, so much as that all software tends to get more complex over time, and distros that are successful tend to ship more and more packages. Note that RedHat nearly doubled its code base in a single year (2000-2001); the Debian figure comes over ten years after that. I'd be shocked if it wasn't a lot bigger than any distro from a decade earlier. That said, Debian (bless it!) does have a tendency to ship everything that will compile.
    – MadHatter
    May 1, 2016 at 8:29

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