The Times has lost almost 90% of its online readership compared to February since making registration mandatory in June, calculations by the Guardian show.

Unregistered users of thetimes.co.uk are now "bounced" to a Times+ membership page where they have to register if they want to view Times content. Data from the web metrics company Experian Hitwise shows that only 25.6% of such users sign up and proceed to a Times web page; based on custom categories (created at the Guardian) that have been used to track the performance of major UK press titles online, visits to the Times site have fallen to 4.16% of UK quality press online traffic, compared with 15% before it made registration compulsory on 15 June.

These figures can then be used to model how this may impact on the number of users hitting the new Times site. Based on the last available ABCe data for Times Online readership (from February 2010), which showed that it had 1.2 million daily unique users, and Hitwise's figures showing it had 15% of UK online newspaper traffic, that means a total of 332,800 daily users trying to visit the Times site.

If none of the people visiting the site have already registered, the one-on-four dropout rate means that traffic actually going from the registration site to the Times site is just 84,800, or 1.06% of total UK newspaper traffic – a 93% fall compared with May.

However, some have registered: Dan Sabbagh, formerly the media editor of the Times, suggests that about 150,000 users registered for access to the Times and Sunday Times while they were free, with 15,000 apparently agreeing to pay money.

If all 150,000 form part of the total 332,800 users going to the site, the fall in traffic is 84% compared with May: 182,800 would be unregistered and "bounced" to the registration site – but only 45,700 would proceed to the site, based on the Hitwise numbers. The total number of daily visitors would thus be 195,700, or just 16% of the February and May pre-registration figures.

News International withdrew in March from the voluntary ABCe auditing scheme, saying only that it had "suspended the public reporting of monthly ABCe website traffic for Times Online and the Sun" and that News International is "working with ABCe to help evolve metrics related to engagement as the business models evolve". But, on these figures, it would now have between 84,800 and 195,700 daily unique users.

The huge drop matches the industry expectation before the Times instituted the paywall that traffic would fall off by 90%, which is the standard experience when a site moves to a paid-access model instead of free access.

The figures are also unlikely to surprise some executives at the Times: the Sunday Times's editor, John Witherow, predicted in May that "perhaps more than 90%" of pre-registration readers were likely to be lost once the registration-only service was implemented.

It is not clear whether the number of people visiting the site will generate enough revenue to justify the experiment – which Rupert Murdoch says could produce "significant revenues" and, if successful, could see other free-access news websites follow suit.

There are approximately 150,000 Times print subscribers who get a free online registration, but if the estimated 15,000 daily online users who agreed to pay opt for the £2 a week deal, the paywall will generate £120,000 a month – £1.4m a year.

Digital revenue should not be seen in isolation to print revenue, however. Sales of the Times have been given a modest boost from the serialisation of Lord Mandelson's book The Third Man, yet News International's accounts to June 2009 show a daily loss of about £240,000 for both Times titles, and last month's ABCs show a year-on-year headline monthly circulation slump of 14%, to 503,642.

Sabbagh goes on to calculate that the typical Times print reader is worth "at least two and a half times" the average online reader.

The Times started redirecting traffic to registration pages on 15 June, and put the paywall fully in place on 2 July.

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