Today’s digital press continues to experiment and struggle with news monetization. But when something that previously cost money becomes free, different questions arise: what made it not-free to begin with, why is it free now, and why isn’t it always free? When and why do publishers circulate news “freely” and what do such moments suggest about these media outlets?

In the most recent study published by the University of Southern California, professor Mike Ananny and USC Ph.D. candidate Leila Bighash looked at when news organizations lower, suspend, or otherwise reconfigure their payment systems to let content circulate unmetered.

Of the 69 instances when paywalls were dropped or eliminated between 1999 and May 2015, there were 41 times that news outlets dropped them only temporarily; the other 28 times, papers made the decision to permanently reduce or eliminate them. Ananny and Bighash were able to categorize these changes in paywall strategy into six different scenarios.

Here are the reasons why publishers drop their paywalls, according to the study:

Public Emergencies

When natural disasters hit their primary publishing regions, The New York Times, The Wall Street Journal, The Baltimore Sun, The Seattle Times, Newsday, Pocono Record, Cape Cod Times, SeacostOnline, and The Day temporarily dropped their paywalls, making either all content or disaster-related information entirely free. Paywalls were also dropped during the Boston Marathon bombing and DC Navy Yard shootings in 2013.

“Such drops and reinstatements are significant because, when news organizations change their paywalls in response to public emergencies and natural disasters, they leave clues about who they think their publishing impacts, what they assume their audiences need, how they see themselves as public services, and when they judge one set of circumstances as sufficiently different from another to warrant a change in news commodification,” the study says.

Planned Special Events

On 8 instances, news organizations dropped their paywalls for events such as political, sport or entertainment events. In 2012, the Financial Times, The New York Times, and The Wall Street Journal provided free coverage around the Election Day. More recently, the FT got rid of its paywall on June 23 when the United Kingdom voted to leave the European Union. Again, the study says these decisions provide insight into an outlet’s news judgment:

“When news organizations drop their election paywalls, they leave clues about what kind of public service they think they should be during elections—what types of coverage are publicly significant enough to be free. And when news organizations drop paywalls for some sports coverage but not others, they reveal which audiences they value, and which events they see as entertaining enough to potentially earn them more advertising over subscription revenue.”

Wider Access

Twelve of the studied drops were described as a desire to give everyone access to coverage considered “too civically valuable to commodify financially, at least for a particular period of time.”

In 2014, for example, the Times gave away a week of free access to its NYT Now app to promote National News Engagement Day. In the same year the Times made NYT Now free to use for all users after there wasn’t enough interest in the subscription app.

“These examples suggest a class of paywall exceptions when news organizations themselves decided to offer free content, and offered reasons for doing so—stating the kind of public services they see themselves providing, and the cross-subsidies they see among their content.”

Advertising and Promotion

Publishers also ditched their paywalls for location-based partnerships or sponsorships. For example, in 2013, Starbucks announced that customers using its store Wifi networks could select 15 free New York Times articles per day from a subset of The Times’s full online site—instead of the standard ten free articles per month for nonsubscribers on non-Starbucks networks. The partnership was later expanded to give members of the “My Starbucks Reward Program” 12 weeks of free access to The Times’s NYT Now mobile app.

Audience Development

The researchers found 17 times when newspapers dropped their paywalls explicitly to grow their audiences. Last year, the Financial Times introduced reduced price paid trials to attract new subscribers. Users could try out full access to the FT for $1. FT CEO John Ridding recently said the paper made the switch to try and build habits among readers.

“The free content resulting from these strategies is a boon to nonsubscribers but—distinct from those driven by emergencies, planned events, access, or advertising—such exceptions use novel content, audience data, and competitor weakness to attract new readers with the aim of eventually converting them into paid subscribers.“

Experimentation

Lastly, there were 11 cases when news organizations dropped their paywalls as they tried to figure out the best way to monetize their content. The Toronto Star dropped its paywall in 2015 when it launched a new tablet app.

“These experiments—their design, success criteria, and the reasons they ended—suggest an ongoing rationale for many paywall drops: learning how and why to configure paywalls in ways that align with an organization’s mission, strategic plans, and audience dynamics,” the study said.

“Exceptions are moments when people exercise power, assert autonomy, and enact ethics. A paywall drop or reconfiguration is an exceptional moment in press economics because it shows how news organizations’ desires to disseminate content freely overtakes an audience’s normal obligation to pay. Paywall exceptions temporarily remove the paywall as an obligatory point of passage.”

The full paper is available here, in the International Journal of Communication.