When web placement was paid per click or per view, Twitter importance was measured by the number of followers you had. Those days are long gone because modern tech savvy social media users understand that engagement is the ultimate measure.
In some cases, people bought Twitter followers to make themselves look better but there are times when those fake followers are added by bots. Why? Because many people automatically follow back all of their followers and these SPAM accounts get a decent following quickly.
The first tool is an online service called the Fakers App. This app allows you to identify how many fake or empty accounts follow you. Better yet, they can perform this same magic on competitors or service providers trying to sell you on their HUGE social media following.
Head over to the webpage (link)
Click on the Connect to Twitter button
Authorize the app to connect to your twitter account. Then let it do its magic
In my case only 3% of my followers are fake. 46% are inactive which isn't surprising knowing how most registered Twitter users rarely tweet. You can use the search box to check this info for someone else
TwitterAudit (link) is another interesting tool that takes a 5,000 follower sample from your account and then creates a follower value score by looking at the ratio of followers to following, number of tweets, date of last tweet, etc.
It creates some interesting graphs:
You'll notice that the stats provided by each site aren't perfectly aligned but they are close. The Inactive status of the Fakers App isn't too valuable for me considering most people sign up and spend most of their time on twitter lurking.
Ultimately less than 3% (in both cases) of my followers are fake. What about you?