The Survey: Which lenses do you use for your Leica M camera? counted in total 142 participants (see for details the link below pointing to Part I of this blog). These participants have reported which lenses they own either by "ticking" the appropriate box in the survey or by communicating them using the so-called "Other" field that was provided. In total, the 142 participants report to own 676 lenses.
As a first result, I have used the data to draw a conclusion on the position of the alternative brands, like Zeiss and Cosina Voigtländer, in the niche market of the Leica users from the forum. As you can deduct from the histogram below most of the 676 lenses are reported to be from Leica (85%) . Cosina Voigtländer is mainly considered the choice for focal lengths not supported by Leica, e.g. 15mm (Cosina Voigtländer Super Wide Heliar 4.5/15). Zeiss lenses only represent about 5%.
As a second result, I would like to share how the owned lenses distribute over the various focal lengths. I have captured the distibution in the picture below. Although I have not yet done the detailed analysis, I find it interesting to see -- confirmed by a quick check on the data -- that while most users own one or more 50mm lenses, they also own a 35mm lens. I personally would have expected that more people would prefer to choose a 28mm next to a 50mm. But obviously, 35mm has a great appeal to Leica M users. Another aspect that I found interesting is that there are multiple participants that indicated to have multiple lenses with the same focal length. But as said, I'll have to do more investigation to get the details documented.