Three of the TV industry’s biggest players are teaming up in hopes of convincing Madison Avenue to accept a different yardstick when it comes to measuring the effectiveness of millions of dollars in advertising.

Viacom, 21st Century Fox’s Fox Networks Group and Time Warner’s Turner say they will all back a single system to facilitate a type of advertising buy that has become more common in recent years as new technology allows marketers to pick and choose the audiences they pitch with a greater deal of precision. Armed with reams of data about customer choice, viewer behavior and digital presence, Madison Avenue has grown more enchanted with “audience buying” deals based on narrower consumer segments – think first-time car buyers, expectant mothers, or orange soda drinkers – that some blue-chip advertisers find more meaningful than the traditional parameters, which largely have to do with age and gender.

“If in fact we are going to move audience-based buying beyond age and sex numbers, this idea needs to happen at scale,” said David Cohen, president of North America operations for Magna,  the Interpublic Group unit that oversees $17 billion worth of U.S. ad spending, in an interview. “It’s a great step forward, and I hope that others will come on board.”

Such an alliance is rare. After all, the three companies work day in and day out to keep ad dollars from going to competitors – like each other. Their convergence might be likened to a scene in the popular film “The Godfather” in which the heads of fierce rival “families” come together at a table to set new policy at a critical moment. To be sure, executives from all the companies said the partnership does not mean Turner, Viacom or Fox will sell ad packages in tandem with the others, just that they will all do business based on the same standard.

The three companies considered the alliance over the past year, said Sean Moran, who heads marketing and partner solutions for Viacom.  Turner, Viacom and Fox have all aggressively touted new brews of data that help advertisers not only pick batches of audience but also determine where, across different programs and outlets, the crowds are most likely to be found. “It all started through relationships and an understanding that these guys really had advances in their data offerings,” Moran said.

The new system is called “Open A.P.,” and the three companies expect to unveil more details at an April 7th event. “While demand for audience targeting has grown significantly, adoption has been limited by the fact that audience buying is not as transparent, as consistent and as easy as traditional guarantees,” the companies said in a letter announcing the venture. “It doesn’t need to be that complicated. That changes today.”

The companies will work with Accenture to standardize how ads aligned with particular audience segments are purchased and to verify delivery of the commercials against their target, according to two people familiar with the matter. Spokespeople for the three companies declined to comment on whether they were working with Accenture, and a spokeswoman for that large consulting firm declined to respond to a query seeking information.

But executives from the three companies, which between them reach 93% of TV viewers through outlets ranging from MTV to TNT to Fox Broadcasting, said they believed the new effort would fill a growing need as digital technology shakes the economy of modern television. With more consumers gravitating to mobile tablets and on-demand streaming video, the main currency of TV – linear audience ratings – has eroded. To keep ad dollars flowing, the media industry needs to find ways to better monetize digital viewers. Striking deals based on more narrowly defined audience characteristics allows the companies to get paid for viewership, no matter the screen in question, and might even let them charge a premium for finding an advertiser’s most likely consumer base.

“The one thing we all were hearing pretty loud and clear from our clients was ‘Oh, if only we could get you all together and see if it could be more simplified and standardized,’” said Donna Speciale, president of Turner’s ad sales division, in an interview. “It really comes from the clients. We are doing this for them.”

Other players are also focusing more intently on audience-based buying. NBCUniversal said earlier this month that it hopes to sell $1 billion in ad inventory from across its portfolio of media assets that will be used to reach specific audiences. Turner’s Speciale has said she hopes 50% of Turner’s inventory will be sold via audience buying by 2020.

“It’s better when the audience is more relevant” to the advertiser “and it’s better for us to be more rated,” noted Joe Marchese, president of advanced advertising products at Fox Networks. “But it’s very hard to buy across the major publishers, the people with the real inventory,” he added. “It just makes sense to make it simple.”

Nielsen, which currently runs the system governing how TV networks and advertisers measure audiences, said in a statement it hoped to work with the new alliance. “”We strongly support the consortium’s efforts to create a clearinghouse to audit the audience-based advertising delivery of its members.  Nielsen’s gold standard data measures many, if not most, of these audience-based advertising guarantees,” the audience-measurement company said in a statment. “We support the consortium’s goals to give advertisers and agencies verified and audited reporting of delivery.  This is an important part of what is needed to create openness and transparency in ad buying and selling.”

Fox, Viacom and Turner unveil the effort just as Madison Avenue prepares for the TV-industry’s annual “upfront” market, during which U.S. TV networks try to sell the bulk of their commercial inventory ahead of the next programming season. Already, media buyers are suggesting the market could be flat to slightly up, but not as robust as the 2016 haggle.

The trio hope other media companies will join them. “Anybody that has ‘C3’ measurement is going to be able to join this consortium,” said Speciale. The TV industry sells ads based on “C3,” or the number of views a commercial break gets alongside a particular program up to three days after it airs. “We believe there are going to be a lot of other hand-raisers,” she said. “That’s what we want.”