More spam graphs

Ken Simpson, CEO of Mailchannels, was kind enough to give me permission to post their graph of spam and email volumes from September 1, 2010 through Jan 3, 2011.

This chart also shows the trend of declining volumes of spam. There are some differences, though, which I think highlight how you get different pictures when looking at different data sources.
For instance, the amount of real mail (blue line) has remained relatively constant over the 4 month period. There was a slight decrease at the very end of the year, but generally real mail volumes stayed constant. Contrastingly, Senderbase shows that while the average daily spam volume fell from 257 billion emails per day to 92.4 billion emails a day and the average mail volume fell from 300 billion to 108 billion.
Each of the graphs I have posted over the last 2 days has a different way to measure and they are actually measuring very different things. I have some ideas on how Senderbase measures things, but I don’t know any of their specifics. I think they’re doing some direct measurement on their servers and using algorithms to extrapolate total volumes and total spam volumes. In contrast, Mailchannels does outbound mail filtering, so what they are measuring is the amount of mail sent by their customers. The CBL measures just volume into a spamtrap and so is a totally inaccurate way to measure real mail.
Given three totally disparate methods of measuring spam show a decrease, I’m pretty confident in saying that there was a real, measurable decrease in spam loads at the end of 2010. But that’s all I can say based on these data. The decrease may be temporary, it may not. Without understanding more I can’t even make any predictions. I will tell you this, though, I’m very interested in seeing what the graphs look like in a month.