Most B2B marketers understand how buying behaviors are changing. As my colleagues have authoritatively written about, business buyers are turning to answer engines as a tool to increase their speed, efficiency, and confidence in purchasing. Accordingly, 90% of B2B marketing leaders report that AI visibility is, at minimum, an investment-level priority.

But the implications of this change in buying behavior are further-reaching than you may realize. A foundational challenge to how B2B marketing operates quietly looms beneath the surface.

Engagement metrics have long dominated how B2B marketing is judged

For more than two decades, B2B marketing has relied on a simple bargain to explain its value: If our business systems can see that buyers engaged with marketing assets, then marketing must be working. Engagement became the simple proof that marketers used to guide investment, defend budgets, and earn credibility with the business.

Forrester’s research shows that the ways B2B marketing presents its business contribution are dominated by engagement-based metrics — metrics such as marketing-sourced pipeline, marketing-influenced revenue, and lead volume. These metrics are all based upon the ability for marketing to “prove” direct engagement with B2B buyers. Eight of the top 12 criteria on which leaders judge B2B marketing are built upon proof of engagement.

Engagement is tangible, it’s relatively easy to measure and describe, and it became an opportunistic way to convey marketing’s value. The problem is that it has never reflected the reality of how buyers buy, what businesses expect of marketing, or what drives organizational impact. And that’s the main reason why so many B2B marketing organizations don’t trust their measurement.

Generative AI search is about to upend this uneasy bargain

When B2B buyers shift a significant portion of their research process to the zero-click answers offered through answer engines, the proof of engagement that B2B marketers rely upon dries up. Over the past months, I’ve spoken with dozens of marketing leaders who’ve experienced web traffic and even demand volume declines of 20–30%. We expect this trend to continue. But the real issue is that, regardless of whether the business is achieving its overall goals and objectives, a decrease in visible engagement will make it appear as if marketing efforts are failing.

This is a precarious position for marketing leaders to be in. The things the business needs most from marketing in this new era (i.e., building buyer preference, gaining visibility in generative AI search) will scarcely show up in engagement data. The more marketing attempts to “perform” against the old objectives, the less progress the business will make in succeeding in a world where buyers embed AI search in their buying process. But continuing to miss objectives undermines marketing’s funding and credibility.

An accountability reset is past due

Engagement-based accountability has never really worked for B2B marketing, but buyer migration to answer engines will fully expose its shortcomings as untenable. Now is our opportunity to rewrite the rules of marketing accountability that works for marketers, our buyers, and our businesses. At Forrester’s upcoming B2B Summit, I’ll highlight the dynamics underpinning marketing accountability, their implications, and how you can build a new approach suited to this era. I hope you can join us.