*Originally posted on VentureBeat

As consumers increasingly use multiple devices in their digital lives, marketers are faced with a problem crippling inefficient advertising paradigms: when they can’t properly attribute ad spend of cross-device marketing to concrete return on investment, they cut the budgets on their campaigns, ruling them ineffective.

But the campaigns themselves aren’t necessarily ineffective. Brands simply can’t accurately track ad performance against revenue.

That’s because advertisers can’t track what devices users have with certainty. The third-party cookie is practically dead. Mobile device usage killed it. There’s a gap between the impact of advertising reach and frequency against multiple touch points.

Regardless of how brands and marketers attempt to rectify the situation, they’re trying to fill a bucket with a hole at the bottom, and it won’t ever be filled — not unless they embrace true cross-device marketing. This begs the question: what does it take to engage in genuine and effective cross-device marketing?

1. Let go of outdated mindsets

Now that the average US household has 10 devices accessing the Internet, it’s time to move beyond the bygone efficacy of third-party browser cookies. They won’t work with browsers that don’t accept them (like smartphones, tablets, wearables, and connected TVs), and won’t be able to track anything outside the browser.

Brands use cookies in conjunction with personally identifiable information (PIIs) such as physical address and geolocation based on IP to essentially make guesses about consumer behavior online. However, the reliability of this probabilistic system is restricted when multiple devices are introduced into the consumer journey of a single user.

For example, marketers tracking cookies in Joe’s PC browser can’t tell if it’s him or his roommate using the PC. The same goes for when they cross-reference geolocation with Joe’s physical address: when his tablet is accessed in his physical address, there’s a high probability that he’s using it. But they can’t be 100% certain.

When Joe switches back and forth between his desktop and mobile devices, it becomes increasingly less probable that marketers are still reaching him and, more importantly, progressively harder to track how ads affect him. The hole at the bottom of the bucket grows bigger.

Marketers also need to throw away assumptions like “mobile doesn’t work” — an incredulous excuse, given that north of 1.7 billion people used mobile devices to access the Internet during the final quarter of 2014, with mobile Internet growth surpassing desktop usage. Wherever consumers are, it’s up to theindustry to make it work. It all works, but everything needs to be put together into a coherent picture.

2. Identify your consumers

What truly cuts across all myriad of devices are registered, logged-in users — actual people that brands don’t have to make educated guesses about using probabilistic (cookie) models.

These users have registered and supplied their names, email addresses, and other pertinent details — along with their consent. The actual identity of the consumer is the magic pill that replaces increasingly ineffective tracking methods and solves consumer targeting and device fragmentation.

In this new model of marketing, made possible by registration-based platforms as well as a variety of social media integration possibilities, advertising shifts from probabilistic to deterministic. Brands knowthey’re actually reaching Joe, what devices Joe uses, and how many times they reach him via which devices.

Innovative digital pioneers like Viant heavily invest in people-based solutions, and this is indeed one of the many ways they have leveraged their MySpace property: confirming consumer identities and eventually linking registration information of users with the devices they use, ensuring that they know the same Joe or Jane is engaging with their touch points regardless of which device they’re using. In Viant’s case, the result is the development of the Viant Advertising Cloud.

The practice itself is still new, but the technology supporting true cross-device marketing is already here. No change in consumer behavior is required – Joe registers and logs in to a variety of platforms every day, from his Facebook and Twitter profiles to his retailer portals where he uses his account for subscriptions, online purchases, and more. Once Joes registers, marketers can place first-party identifiers on the devices he uses to access the web — and know for sure that they’re tracking the same Joe even when he logs out.

And it all starts with genuinely identifying the consumer.

3. Track the right metrics

Brands and marketers need to ask the right questions and track the right metrics to ensure effective holistic cross-device marketing.

According to the IAB and Winterberry Group, over 90 percent of marketers use five or more distinct tool sets to support their data-driven campaigns. True cross-device marketing doesn’t need to rely on a web of interconnected tools and service providers, as all this does is dilute the data each time it’s passed over and kills a large portion of the marketing budget. Instead, marketers should be implementing a single management platform as the central control center of their advertising.

Next, they need to track more robust, reliable key performance indicators, such as reach and frequency. They need to accurately manage what ads are shown to Joe on which devices and how often.

Tracking reach and frequency across all devices maximizes ad spend and minimizes inefficient performance attribution, finally plugging the leak at the bottom of the bucket.

Along with reach and frequency, brands should monitor Joe’s path to purchase. They need to gain a comprehensive understanding of his multi-touch journey. They need to track which ad formats across which devices influence purchase decisions. It is crucial they see the ROI of ad spend as the number of Joe’s touch points increases.

The ideal advertising experience was once only a dream: hit Joe with a TV ad before leaving home, then again on the radio along the highway to work, then with a billboard as he pulls into his office building, and finally, through word-of-mouth as a coworker mentions brands at the water cooler. Now brands and marketers can do just that in the proper and modern way across Joe’s multiple digital devices.

Cross-device marketing is the realization of this multi-touch ideal for an online world, one that guarantees brand awareness through effective cross-device storytelling — and where ROI against ad spend isn’t based on just probability and cookies.