Hello,
I recently discovered that bridges report detailed bandwidth histories in their extrainfo descriptors.
We should think about the privacy implications of these statistics since they are quite fine grained (multiple measurements per day) and some bridges don't have many clients (hence small anonymity set for them).
Until then, I decided to visualize a bit those bandwidth histories, to better understand how much bridges are used. This took a bit longer than I expected, so I'm just going to show you some preliminary results. Here is a graph!
https://people.torproject.org/~asn/bridges_bureau/bridges_daily_bandwidth.pn...
To generate this graph, I summed up the reported bandwidth histories of each bridge descriptor to get that bridge's daily consumption. I used the number of *read* bytes, and ignored the number of written bytes. I discarded multiple descriptors of the same bridge and bridges which did not report 24 hours worth of bandwidth history. I started with about 7603 descriptors, in the end the graphs include about 4k bridges.
Basically, this graph tells us that only very few bridges see big amounts of traffic. Most bridges are concentrated on the left side of the graph. If you can't see how many bridges contribute big bandwidth because their column is so small, you can use those spikes that come from the bottom of the graph. Each such spike is one bridge.
The graph is in megabytes, and its left side is too crowded. Here is another graph that might be cleaner:
https://people.torproject.org/~asn/bridges_bureau/bridges_daily_bandwidth_pr...
This graph was created the same way, but I discarded the 200 highest observations. This makes the left hand side of the graph cleaner. Here we can see that most bridges see less than 50 MBs of traffic per day, and there are even a few hundreds of them who see none or almost none.
Unfortunately, this concludes my studies for today. Maybe in the future I will work on this a bit more, and also take in account the pluggable transports that these bridges use as well as how many hours in a day each bridge did not have any activity.
Questions and feedback on my methodology are welcome. If people want to work on this, I'm happy to clean up and publish my Python scripts.
Cheers!