(I begin this post as a reply to a comment from and then decided it merited a full post.)
Here are some possible interpretations of “The statistics about reading are particularly discouraging: The average software developer, for example, doesn’t even own a single book on the subject of his or her work, and hasn’t ever read one.” (From Peopleware, by Tom DeMarco and Timothy Lister.)
Divide the number of copies of programming books ever sold by the number of people writing code today and you will get a number less than 1.
Fewer than 50% of programmers own one or more programming books.
One of the above in combination with the stipulation that the book is directly related to what the programmer is working on right now.
Mary Gardiner points out that any programmer who took a course probably had to buy a programming-related textbook. It’s not unthinkable that the student (a) didn’t read anything like the whole book, (b) sold or threw away the book immediately after the course. In fact, I will guarantee (a). Also, plenty of working programmers never took a programming or computer-related course.
Note also that this statement was made in 1999. Perhaps things have changed.
I still want a source for this statement and have been googling around a bit to find my own statistics. Joel on Software says that the market for programming books is miniscule compared to the number of programmers in the world but doesn’t give any numbers to back it up, so strike out again.
O’Reilly says that English language computer book sales were around 7,000,000 copies in 2006 and appear to be declining. I’ll wildly estimate that computer book sales prior to 1995 were negligible, that 1995 – 2000 was 2 million books, 2000 – 2005 was 20 million books, and that 2005 – 2008 was 18 million books. So 40 million computer books total sold. I’ll estimate that 30 million of them went into the trash shortly thereafter, for 10 million computer books in the possession of a human today. I’ll say that 80% of those books are in the possession of programmers, for 8 million computer books in the possession of a working programmer. (Right now I would be passing the how-many-piano-tuners-in-Chicago question at a programming interview – if I hadn’t already stopped the interview and left.)
The U.S. Department of Labor says there were about 850,000 software engineers in the U.S. in 2006. However, I am certain this is a major underestimate; for example, this week I attended a meeting with a bunch of Wall Street IT people. One of them said, “We’re fooling ourselves, we’re all in the business of writing software.” Their business advantage at this point is based entirely on the in-house software they write, and it’s written only occasionally by people with the title of software engineer. Intel was like that too – all those “hardware engineers” are writing VHDL all day, not to mention simulators and optimizers and BIOSes, etc. The sciences are filled with non-software engineer programmers – so much work is done as simulation or processing of huge volumes of data. I’m going to grab a number out of the air and say there are 2 million programmers in the U.S., and that that represents, oh, 2/3 of the total world population of programmers. So around 3 million programmers.
So, call it 3 million programmers and 8 million programming books owned by said programmers. However you slice it, interpretation number 1 of the statement (books/programmers < 1.0) doesn't work out. So it would have to be based on the median rather than the mean.
It comes down to how Zipfian the distribution of programming book ownership is. I recently went through a major purge and kept the 20 computer books that I have ever read or referenced out of something like 40 – 50 total. (Bye-bye, Java in a Nutshell!) Let’s say that 90% of computer books are owned by 10% of programmers – totally reasonable – and you end up with about 1 million books to distribute amongst the bottom 2 million programmers. If they were completely evenly distributed (and they aren’t) you’d have 45% of the programmers without a single book. So 50+% of programmers not owning a single programming book kinda works given my wild estimates.
I am never writing a computer book.
P.S. Refinements on these numbers are welcome!
P.P.S My previous post on Peopleware is currently the 14th result on Google for “peopleware”. That’s disturbing.