Hitwise has announced that the market share of visits to Twitter surpassed Digg for the first time since launch.

In the US, the micro-blogging site was ranked number 84 (above Digg at 85) in the "Computers and Internet" category.

Hitwise partly attributes the rise in traffic to the US Airways plane crash in to the Hudson River last Thursday, that saw many posts and updates about the situation as well as the publicity one photo of the plane taken by a Twitter user Janis Krums, generated.

Hitwise notes that one major shift is the increased traffic to Twitter from internet users aged 25-34 which now accounts for 45% of use compared to 12% this time last year.

Here in the UK internet traffic to Twitter has increased nearly 10-fold over past last 12 months with traffic to the site up 974% since January 2008.

In the UK the fastest growing age group of users is 35-44 year olds, who account for 17.3% of UK visitors.

Noting that "many people seem to find Twitter addictive", Hitwise's Robin Goad says these numbers will actually be a low estimate as to how many use the service as many do so through mobile phones and third party applications such as Twitterrific, Twitterfeed and Tweetdeck.

It might be possible that Obama's inauguration will have kept the figures high this week too - Twitter said the site saw fives times the normal tweets-per-second as the new president was signed in.