It’s common knowledge that the business model for newspapers started going awry in a major way with the decline in newspaper classified advertising.

Craigslist played a huge role in that development, as the online classifieds site went about methodically entering one urban market after another across the United States.

And now we have quantification of just how impactful Craigslist’s role was.  It comes in the form of a May 2013 study authored by Robert Seamans of New York University’s Stern School of Business and Feng Zhu of the University of Southern California.

Titled Responses to Entry in Multi-Sided Markets:  The Impact of Craigslist on Local Newspapers, the study explored the dynamics at play over the period 2000-2007, focusing on newspapers’ degree of reliance on classifieds at the time of Craigslist’s entry into their markets.

What the researchers found was that those newspapers that relied heavily on classified ads for revenue experienced more than a 20% decline in classified advertising rates following Craigslist’s entry into their markets.

But that isn’t all:  The outmigration of classified advertising to Craigslist was accompanied by other negative trend lines — an increase of subscription prices (up 3%+) and lowering circulation figures (down nearly 5%).

Even newspaper display advertising rates fell by approximately 3%.

Were these developments “cause” or “effect”?  The study’s authors posit that fewer classified ads may have diminished the incentive for people to purchase the newspapers.  Also, display advertising rates tend to track circulation figures, so once the “decline cycle” started, it was bound to continue.

The study concludes that by offering buyers and sellers a free classified ad alternative to paid listings in newspapers, Craigslist saved users approximately $5 billion over the seven-year period.

Those dollars came right out of the hides of the newspapers, of course … and changed the print newspaper industry for good.

But here’s the thing:  The experience of the newspaper industry has relevance beyond just them.  “The boundaries between media industries are blurred and advertisers are able to reach consumers through a variety of platforms such as TV, the Internet and mobile devices,” the authors write.

The unmistakable message to others in the media is this:  It could happen to you, too.

A full summary of the Seamans/Zhu report can be found here.