How many inactive accounts does Twitter have?

When Twitter filed for its initial public offering on Oct. 3, it stated that it had 218.3 million average monthly active users in the three months ended June 30.
What it didn’t reveal was how many total accounts it has. Without that figure, we can’t determine how many people have signed up for the service and quit.
All Things D reported last month that Twitter has more than 1 billion registered accounts and that only a quarter of that number are repeat Twitter customers. That’s a lot of Twitter quitters.
One problem with its monthly active user figure of 218 million is that an unknown number of those are spam accounts or multiple accounts of individual users.
I’ve had four Twitter accounts in the past (two for work and two personal), but now I’m down to one personal account.
Then there are the problems of spam accounts and fake followers.
Many Twitter accounts are set up by people, often shady, to sell products and services. These spammers show up as followers, in mentions and when you do searches of popular subjects.
Some businesses even sell fake Twitter followers so people can appear to be more popular, as the New York Times and the Wall Street Journal reported.
Twitter says “false or spam accounts” make up less than 5% of the social network’s monthly active users. If it’s close to 5%, that would be nearly 11 million fake or spam accounts.
A group called StatusPeople created an app for determining how many of your Twitter followers fake or inactive.
Of my 661 Twitter followers, 76% are real, 8% are fake and 16% are inactive, according to StatusPeople.

Photo: My Twitter follower report from StatusPeople.