VIC Consulting Twitter Analytics - http://www.vicconsult.com/twitter-follower-statistics-reports-analytics/
Number of Tweets/Updates Users
less than 1000 638
between 1000 and 5000 302
between 5000 and 10000 123
between 10000 and 20000 112
between 20000 and 50000 73
more than 50000 42
1290