An invite-only conference began today at the American Press Institute with a singular directive: “generating revenue from online content.” At the morning session, which just wrapped up, Greg Harmon of Belden Interactive and Greg Swanson of ITZ Publishing presented their survey of 2,400 U.S. newspaper executives. The cardinal finding, first reported this morning by Alan Mutter: 51% think they can successfully charge for content on the Internet.

I honestly have no idea what to make of that number, but there’s a ton of really useful data in Harmon and Swanson’s research, including some online revenue figures and in-depth traffic statistics for newspaper websites. The API has kindly posted their 80-slide presentation, which you can follow above.

If you do, the essential accompaniment is Bill Densmore’s liveblog of the presentation, below. (Densmore is a founder of CircLabs and the Media Giraffe Project.) You’ll also want to apply a helping of salt because ITZ Publishing consults for Steve Brill’s pay-for-news firm Journalism Online, which just touted the results as an “API study” without noting its business interest.

Here are some datapoints I found interesting:

— In nearly all markets, newspaper websites receive 2.5 visits and 10 pageviews for each unique visitor.

— “Core loyalists,” who visit a newspaper 2-3 times a day for 20 days a month, comprise 25% of unique visitors. Not surprisingly, then, core loyalists account for 86% of pageviews and are “overwhelmingly local.”

— Seventy percent of core loyalists online are also readers of the print edition (meaning they subscribe or they picked up a copy in the past seven days).

— Newspaper sites made next to no revenue from behaviorally targeted ads or local search advertising in 2008.

— Classified advertising accounts for 16% to 22% of online revenue for newspapers, though that’s expected to decline this year.

— Most newspapers are selling roughly half of their online advertising inventory, but small newspapers only sold 29% in 2008.

What to make of all that? Harmon and Swanson pursue several arguments that you can follow in the slides and Densmore’s notes. I think it’s particularly noteworthy that 70% of those core loyalists online are also print readers, but others can decide what that means for the newspaper industry.