It's been two years since Nielsen first began developing a tool to measure viewers across all platforms—not just TV watchers as it has for the last 65 years. Since then, however, the project has attained mythical status among many advertisers, buyers and network executives. "I'll believe it when I see it," more than one has told me dismissively in recent months.

But the wait is almost over. Nielsen is putting the finishing touches on total audience measurement and gave Adweek an exclusive look at its new multiplatform measurement tool, which it says will forever change the industry. The company will begin sharing data with its clients this December and roll out the tool's full capabilities early next year.

To paraphrase Seinfeld, total audience measurement is real and, given the industry's growing cries this fall (in the face of more live TV viewership declines) for a tool that will finally allow them to fully measure and monetize viewers, it's spectacular.

Nielsen has spent two years working on the framework, as it worked to align the disparate metrics for video content. The company has long had the capability to measure ratings up to 35 days after live airing, for both linear and digital TV. But evp Megan Clarken, who is leading the project, said this is over and above anything Nielsen has ever compiled. "What we have to do to perform a cross-platform total audience measurement is line all of those numbers up, so they have to be apples-to-apples comparisons," Clarken said. "They have to follow the same underlying rules. They have to be on a single-sourced platform, because otherwise you're cobbling numbers together and creating Frankenmetrics."

The result is total audience measurement, Nielsen's single-sourced platform to account for all viewing across linear TV, DVR, VOD, connected TV devices (Roku, Apple TV and Xbox), mobile, PC and tablets. The only thing left out: streaming content on wearables like the Apple Watch. "There's always going to be things that are so small for us right now," said Clarken.

"What we're acutely aware of is our measurement underpins $70 billion worth of advertising," she added.

While TV ratings would indicate that television viewership is in continued decline, especially this fall, "video viewing is actually relatively flat, but it's moved," said Clarken, as audiences continue to shift from live TV to watching VOD and connected devices or streaming them via mobile or tablet devices, which are not measured in the industry's standard C3 and C7 ratings metrics. Digital first providers like YouTube and AOL have also been shut out. They will now be included.

An early test of Nielsen's total audience measurement reveals just how much of a program's audience is overlooked by the current C3 and C7 metrics. For one client's broadcast drama that aired in early September, Nielsen found the following:

45 percent of the episode's audience watched during its live airing

An additional 32 percent watched it via DVR during the first seven days after it aired

2 percent watched on DVR between 8 days and 35 days after it aired

7 percent of the audience watched it on VOD from within 35 days

6 percent watched via a connected TV device

8 percent watched digitally, streaming it on a PC, mobile device or tablet

Notably, among the adults 25-34 demographic, only 15 percent watched the episode live (compared with 64 percent of adults 50 and older). Of that same 25-34 demo, 22 percent used a connected TV to watch the show, and 18 percent watched it digitally, the highest of any demo.

"No longer are [networks] just stuck with [live viewers]," said Clarken. "Through total audience, we're now picking up all of their viewing across DVR, VOD and connected TV, and able to add that together so they can get a real sense of their audiences, and not just be restricted to reporting out or talking about their live audiences. Live and DVR is very dominant in the older demographics, very less predominant in the younger demographics, so being able to measure that is extremely valuable."

Meanwhile, other shows will discover that they are not as popular across all platforms. Another Nielsen client asked the company to measure its audience across digital devices only to learn that its lift is minuscule. "What this does for them is it tells them that and it allows them to reset their strategies" to reduce dynamic ad load, said Clarken.

The total audience measurement tool, which will roll out late in the first quarter of 2016 (Nielsen will begin to share data with clients in December, allowing them full access to the tool), will allow users to break down programs by categories like unique audience, reach, gross average minute audience (both in viewers and GRP—gross ratings point, where one GRP is equal to 1 percent of TV households), minutes viewed and frequency (the average number of exposures to a show or network). Users can search across a variety of demos, date ranges and platforms.

The tool will include AOL and YouTube alongside the networks. "For total content ratings, we want to have like-for-like, level playing field. Everybody can get measured, and the objective is to have that complete view, regardless of how they're monetized," said David Wong, svp, product leadership.

With the tool, users will be able to track the overall performance in a selected date range and all the views that are coming to that network. "We're still tied to this old-fashioned, telecast-oriented view—the broadcast time," said Wong. "The approach we're taking here is, 'Tell me what happened last week. I don't care what program it was or what telecast it was. I want to know what happened last week.' The idea is that we're shifting to start to provide that view of all the consumption, across a particular asset, network or episode that consumers are viewing."

Nielsen can also "de-duplicate" the total numbers, removing duplicate views by the same person on different platforms, revealing the total unduplicated audience (which will, of course, be lower than the duplicated audience, given that some viewers were counted multiple times). "This is very powerful, particularly for advertisers, when you're trying to make sure that you're managing frequency, you're capping the amount of times they've seen an advertising campaign," said Clarken.

For specific episodes, users can see how it performed over a specific date range and take into account repeat airings of an episode, VOD playback and its performance on other platforms like a network's websites and apps and SVOD platforms like Hulu.

"It is going to help our clients not only be able to value their media assets, but be able to demonstrate what the value is to marketers and to the marketplace, how much interest there is in their media, but it will also help them to make better choices about how to evolve the currency. Because it gives them the flexibility to start to say, 'What really happens when I put an episode out there? What does the life of an episode look like after it first hits, and then it becomes available on multiple platforms and the windows start to open up.' This will give all the texture to a consumer behavior around a particular show," said Wong.

While the tool has created comparability metrics among the various platforms, "that doesn't mean we're going to ignore the metrics which are relevant to a particular platform" like viewability, said Wong.

While Nielsen is often criticized for its inability to fully measure audiences, the company says its hands have been tied as it was forced to adhere to the C3 and C7 metrics agreed to in 2006. Those metrics discount any viewing beyond seven days, most mobile viewing and any content with different ad loads than the original broadcast.

In addition to its panel of 20,000 households (which will be doubled this January to 40,000 households or 100,000 people in total), Nielsen has been working with media owners and MVPDs (cable and satellite providers) to install its software development kit (SDK) on their various apps and players. "Panels are never going to be big enough, so we use census measurement so that we can accurately collect every single thing that happens as it happens," said Clarken.

When Nielsen's SDK is installed on apps and software, the company is alerted when any machine accesses video content. Nielsen then aggregates the device IDs and passes them along to Facebook, which has 180 million device IDs and uses a "blind match," per Clarken, to attach age and gender and sends that data back to Nielsen. (Users can opt out on their respective devices.)

"Then, at the end of the day, it's always the single-sourced TV panel that connects that data, calibrates it and makes sure it looks right," said Clarken. The panel then helps Nielsen determine, for example, which video views should be applied to kids who aren't allowed to have Facebook accounts.

When total audience measurement rolls out in December in what svp Kelly Abcarian calls "a private industry preview," clients will only be able to view their own data but won't have full use of the tool and can't see how their content stacks up against others. Then, late in the first quarter of 2016, all clients will have access to the tool, which will allow them to see each other's performance.

Total audience measurement comes as Nielsen is under more pressure than ever to deliver a multiplatform tool. Several companies, including Symphony Advanced Media, have crated tools of their own they hope will allow then to overtake Nielsen as the new ratings standard. On Sept. 29, ComScore announced it will acquire Rentrak in an effort to take on Nielsen.

Clarken said Nielsen's rollout has nothing to do with the recent moves by its competitors. "We're focused on getting the service out into the marketplace as fast as possible," she said. "A disaster would be if you get that wrong or you went out too soon. We have the burden of responsibility to make sure that as fast as people want this, it's more important that it's introduced in the market in a way that's not disruptive to $70 billion worth of advertising."