• by Erik Sass  @eriksass1, January 3, 2011

After a strong start following the debut of Apple's popular iPad in April 2010, sales of digital magazines on the tablet computer have fallen significantly, according to data from the Audit Bureau of Circulations analyzed by Women's Wear Daily.

Some of the biggest drops came at Wired magazine, a seemingly natural fit for the iPad audience with its futuristic tech focus. Although the medium is touted as a lifesaver for publishing, it may take time to kick in. For now, from over 100,000 digital magazines for Wired's first digital iPad issue in June, sales slumped to 31,000 digital copies in September, followed by 22,000 in October and 23,000 in November, per WWD.

Similarly, Vanity Fair slumped from 10,500 digital magazines sold in August-October to 8,700 in November. In addition, Glamour slid from 4,301 copies in September to 2,775 in November. After averaging roughly 13,000 digital magazines sold from May-October, GQ slid to 11,000 in November.

It's not quite clear what's behind these declines, or what they mean for the long-term prospects of magazine publishers. One likely factor driving magazine sales in the early days of the iPad boom was the simple novelty of the tablet computer itself, as well as the digital media tailored for it.

It's worth noting that digital ads delivered to iPads during the first flush of novelty scored much higher than online display ads delivered to desktops and laptops in click-through rates and other measures of engagement.

Still, most industry watchers expected these impressive figures to subside as the ads, like the device, became more routine for users.

On the other hand, the decline in iPad magazine sales is more alarming, considering the rapid expansion of the potential market over the same period. The total number of iPads sold jumped 565% from 2 million at the end of May to an estimated 13.3 million by the end of the year. Yet iPad magazine sales have not only failed to scale up in comparable fashion -- they have declined, often by double digits.

One major hurdle: many magazine and newspaper publishers say they are discouraged from offering digital subscriptions for the device, given Apple's reticence in sharing consumer data -- like the geographic location of iPad owners -- which makes it hard to market subscriptions to likely buyers. So far, most publishers have confined themselves to selling single issues.

Also, publishers want to retain control of their subscriptions and users personal information. Conversely, Apple wants a piece of the customer pie. It has offered publishers 70% of each sale and the ability to sell subscriptions through iTunes and offer subscribers an opt-in form to give publishers their personal information, per AllThingsD. A few pubs -- Newsweek and People -- are available now, says the online magazine, but that's a tiny fraction of what could be on iTunes.