Some 87% of publishers in North America have iPad apps and, while only 22% say their mobile and tablet apps are profitable, 51% expect these apps to bring in money over the next two years.

Such are the findings of the Alliance for Audited Media’s annual publisher survey on digital practices, which demonstrate how important tablet devices – and specifically the iPad – have become for the sector: the number of publishers with iPad apps in 2012 is greater than those with apps for iPhone (85%) and Android (75%).

Meanwhile, apps for Kindle and Nook are growing steadily: 67% of publishers have Kindle apps, up from 24% in 2011, while the number of publishers with Nook apps grew from 14% last year to 57% in 2012. Overall, 90% of respondents have a mobile presence of some kind, up from 51% in 2009.

Publishers are more like to charge for content on the iPad (56%), followed by the iPhone at 42%. Half of respondents said their websites were profitable today, although just 22% of apps bring in a profit.

Paywalls are also on the rise: 48% of newspaper respondents said they have some kind of paywall, with metered paywalls the most popular.