I love books, and am quite fond of my little collection of knitting and crocheting books and magazines. While printed and electronic patterns are nice, I cannot plunk them on the table to browse through while I eat dinner. However, pattern books are expensive, and as an American living in Belgium I would need to import English-versions to get something I could use, and would then need to port heavy books with me whenever I move again. Every debate as to what book I would like to buy involves me trying to estimate how useful I would find the book and asking if it is worth the money.
Qualitatively, I can evaluate a pattern book by looking it up on Ravelry and counting how many patterns appeal to me. But I am a scientist and I like numbers, and I wanted a more qualitative way to judge the usefulness of a book, so I tried to calculate it. Whether or not the quantity I chose is a good representation of a book's usefulness is debatable, which is part of the scientific process as well.
Ravelry doesn't have its own app, but it does make its API available to developers who want to access Ravelry's information. I wrote a macro (and learned how to query websites with python in the process!) that generated lists of how many projects and how many patterns users had made from a given book of patterns. Then I made histograms like this:
The blue histogram on the left is the number of projects per user made from patterns in Socks from the Top Up. The average number of projects per user is 2.22, though some dedicated souls have made more than 40 projects from this pattern collection. As four of the 23 patterns in Socks from the Top Up are available for free with three of them being basic sock recipes, it probably shouldn't be surprising that users reuse these patterns. Still, as I was interested in what percentage of the book was useful, I made the green histogram on the right. This one shows the number of patterns used from the book by each user, so it is essentially the histogram on the left with duplicate projects removed. The average number of patterns is accordingly a bit lower than the average number of projects, at 1.82. With 23 patterns in the book, that means that on average, a user uses 8% of the pattern material.
I made the calculations described above for several sock pattern books, because those are the ones I am thinking about the most at the moment. You can see the results of all of these calculations below. Note that Knit. Sock. Love isn't included. I wanted to include it, because it contains four or five sock patterns that I think are lovely, but it also contains the Monkeys. There are more than 18000 pairs of monkeys listed on Ravelry, and my macro capped out at handling 10000 projects, with my current API skills being insufficient to figure out a work-around.
That the average number of patterns used is close to constant, between 1 and 2 patterns, was surprising to me because these books vary quite a bit in size. That's why the last, dark green graph is so spiky compared to the others; it shows what fraction of a book's patterns was used on average. Sock Innovation is relatively small with only 17 patterns, and as users tend to make 1-2 of the patterns, that means the usage is around 12%. Think Outside the Sox has 63 patterns, but users still tend to make 1-2 of them, which means the usage is close to 2% of the available material. Clearly, buying a large book of patterns because the price per pattern is less isn't accurate thinking, because the average amount of a book used is the same regardless of the book's size.
You might be the exception to that, of course; I currently own Socks from the Toe Up, and have made four pairs of socks from its patterns with a fifth on the needles as I type, which is two, almost three pairs of socks above the average for that book. That is where knowing one's personal use patterns is more useful than knowing averages across many users. Still, one can conclude that of the books considered, Sock Innovation provides the most material that actually gets used by those that purchase the book.
I still wish that I could add Knit. Sock. Love, though. Maybe I'll include it but skip over the Monkeys. I'm not interested in making that pattern anyway.