Is Twitter Usage Really Falling?

TechCrunch reported today that the number of US unique visitors to Twitter’s Website was off 8% in October compared to September. Twitter.com had 19.2 million uniques in October, down from 20.9 million in September, according to comScore. But until Twitter or some outside measurement firm can capture total activity on Twitter, including all the tweets that come via clients such as TweetDeck, Seesmic or CoTweet, any discussion of Twitter’s health is going to be faulty.

According to the TechCrunch article, Twitter is working hard to make its Website more interesting.

CEO Evan Williams recently acknowledged the slowdown in the U.S., and hopes that a slew of new features will help revive growth to the site. Many of these features are already rolling out, including the new Retweet button, Lists, and Geolocation features.

Twitter is obviously committed to making its service better on its own Website (these numbers do not measure usage on mobile or desktop clients, which is easily half of all Twitter usage). But while it fiddles, rival Facebook keeps moving further and further ahead.

While it’s valuable to look at Twitter’s Web traffic, the true picture won’t emerge until all the third-party traffic from mobile phones and API clients is accounted for. And it’s likely sizeable.

According to Crowd Science’s August 2009 survey of Twitter users in the US, while 71% said they primarily accessed Twitter via the Web, 26% said their primary way of accessing Twitter was via a third-party application.

And of people with only one Internet-connected device, just 10% use Twitter or another status update service, according to the Pew Internet & American Life Project’s recent report. But among people who have at least four Internet-connected devices (such as a mobile phone or game console in addition to a PC), 39% use Twitter or another status update service.

Who’s tracking Twitter’s non-Web usage? Add a comment to this post if you know of a company working on this. I’d like to learn more.

Update: TechCrunch cites data from PingDom saying that US Twitter users sent an average of 27.3 million tweets per day during the three weeks ended Nov. 11. While that data doesn’t say anything about the number of users Twitter has, it does show that they are quite active. (No word on what percentage of the tweets were spam, however.)