September's US ComScore data has just been released and it appears that the number of unique visitors attracted to the website is flat-lining.
However, the numbers should be treated with a measure of caution as the report only measures traffic pulled in by the main URL twitter.com.
The ComScore stats do not measure traffic on third party apps such as TweetDeck, which users access to monitor and publish tweets. Twitter's audience, therefore, is potentially much larger.
According to the figures, traffic to Twitter.com barely grew in September despite expectations of a spike in traffic as people returned to work from summer breaks.
In August, Twitter received 20.8m unique visits in the US compared to 20.9m unique visits in September.
By comparison, Facebook's unique monthly visitors grew by a greater margin over the same period, up from 92.2m unique visitors in August to 95.5m unique visitors in September.
Facebook's audience could be set for a boost with the launch of a stripped down basic version in August called Facebook Lite.
The idea behind the launch is to enable internet users in countries with slow broadband speeds such as Brazil to sign up and join the social network.