Don’t call it a “micro” blog: Twitter continues to grow by leaps and bounds, in terms of number of users and tweets per day, as well as other measures like frequency of log-ins. However the average number of tweets per user appears to have mostly held steady -- although that may be changing in recent months.
The total number of accounts registered on Twitter, worldwide, has steadily increased from around 75 million in January 2010 to 145 million in July 2010, 240 million in January 2011, and 300 million in May 2011. Assuming growth has continued on this trajectory, Twitter may have reached 360 million registered users today.
Meanwhile the total number of tweets per day has grown from 35 million in January 2010 to 55 million in July 2010, 110 million in January 2011, 140 million in May 2011, and 250 million today, according to Twitter CEO Dick Costolo.
Two things stand out from this data: first, most registered Twitter users aren’t active users. Second, dividing the number of tweets per day by the number of registered users, the number of daily tweets per user has mostly remained steady, fluctuating from around .47 in January 2010 to .38 in July 2010, before returning to .46 in January 2011 and .47 in May 2011.
However the jump to 250 million tweets per day currently may represent a big increase, depending on the total number of registered users added since May of this year. Unfortunately I can’t find reliable data for the total number of registered users today, but even assuming that Twitter managed to add 100 million users in the last five months, the proportion of daily tweets per user would have rocketed to .625.
Defining "activity" by messages "sent" is misleading. Twitter is also for receiving messages. In fact, much of what counts in the media world is concerned with receiving messages, not sending them. No one holds YouTube to the same standard as Twitter, so it seems unfair to focus on messages being sent.
Useful, too, to remind ourselves that the studies are clear that average tweets don't mean much. Twitter's profile is that core superusers send the vast majority of the tweets. I seem to recall numbers like 8% of users are responsible for 90% of tweets. But that probably has some exaggeration in the % of tweets.
But this also supports Doug Ferguson's thought. Because it means that 90% of the users are primarily lurkers (active or not)...