First - there was Analytics, then there was Attribution - first, last, data-led, evenly-weighted and whatever else. All of this to cover up a fatal flaw - none of this really tells you the value of your advertising.
In today’s complex digital advertising environment, understanding how to attribute success to the right channels and tactics can be a challenge.
Only marketing incrementality testing can really prove the value of your marketing channels and messaging.
In this article, we’ll explore why incrementality beats attribution, why the last-click model is bad for your business, and what you can discover through incremental testing.
Why Incrementality Beats Attribution
Attribution models, while commonly used in digital marketing, are essentially methods of assigning credit to different marketing touchpoints along a customer’s journey. Whether you use first-touch, multi-touch, or last-click attribution, these models attempt to explain which parts of your marketing funnel are driving the most conversions. However, this approach can miss the bigger picture.
Example: Imagine you’re running a Facebook ad campaign for an eCommerce store, and a user clicks on your ad but doesn’t convert. Later, the same user finds your website through Google Search and makes a purchase. A last-click attribution model would give full credit to Google Search, while completely ignoring the role of your Facebook campaign in influencing that decision. This is where incrementality testing shines.
Incrementality testing answers a critical question: What impact would your marketing spend have if it didn’t exist? By running controlled experiments, typically using holdout groups (where some users do not see your ads), marketers can measure the true lift generated by their campaigns.
With an attribution model, you're making assumptions about the role of different touchpoints. Incrementality testing, however, removes assumptions and focuses on actual outcomes, allowing you to understand the genuine contribution of each marketing activity.
At Growth(by)Gardner, for example, we ran a marketing incrementality test for a tech SaaS client looking to scale their customer acquisition. While attribution suggested that paid search was driving most conversions, our incremental analysis revealed that organic channels were doing a significant amount of heavy lifting. This insight allowed the client to better allocate their budget, shifting resources from paid to organic efforts, which ultimately increased their overall ROI by 34%.
Is a Last-Click Attribution Model Is Bad for Your Business
The last-click model is one of the most commonly used attribution models. It gives 100% of the credit for a conversion to the last touchpoint a customer interacted with before making a purchase. On the surface, this seems straightforward—after all, the final interaction could be the one that tipped the scale toward conversion. However, it doesn’t account for the many other touchpoints that likely influenced the customer’s decision.
Relying solely on a last-click model can lead to several negative outcomes for your business:
Overinvestment in conversion channels: Since last-click models tend to favor direct response channels like Google Search or remarketing, businesses may over-invest in these areas, mistakenly thinking they are the sole drivers of conversions. This leads to an imbalanced budget and a missed opportunity to invest in higher-funnel activities like brand awareness or content marketing.
Undervaluing awareness and consideration phases: Branding and upper-funnel efforts are often the first touchpoints a customer has with your brand. By focusing on the last interaction, you miss the opportunity to understand how these efforts build awareness, nurture interest, and eventually drive conversions.
In short - the biggest risk is that you'll focus so much on channels that convert that your "funnel" won't be filling up - and you'll only be competing for customers at the most expensive point, that point of conversion. This will make your marketing incredibly expensive and growth will be difficult to scale.
Example: A popular eCommerce brand I worked with found that their last-click attribution model consistently undervalued their social media marketing efforts. Facebook and Instagram ads were playing a crucial role in introducing new users to their brand, but since these users often converted later through a search ad, the last-click model gave all the credit to Google Ads. Through an incrementality test, they discovered that their social campaigns were responsible for 40% more conversions than previously thought, which led to a reallocation of budget and improved overall performance.
By shifting away from the last-click approach, businesses can focus on building a comprehensive marketing strategy that acknowledges the full customer journey.
What You Can Discover with Incrementality
Incrementality testing doesn’t just help with budget allocation—it offers a wealth of insights that can transform how you approach your entire marketing strategy.
Channel effectiveness: One of the most important insights you gain is a clear understanding of which channels are truly driving growth. For instance, if you’re running email campaigns, social ads, and search ads, incrementality testing will reveal whether your email list is genuinely driving incremental sales or whether it’s mainly reaching users who would have purchased anyway.
At Growth(by)Gardner, we worked with an automotive publisher that was heavily invested in display advertising. While their attribution model suggested this channel was generating conversions, incrementality testing showed that 60% of those conversions would have happened without the ads. Armed with this knowledge, they reduced their investment in display ads and saw a 20% increase in return on ad spend (ROAS) by reallocating the budget to more effective channels.
Incrementality helps understand the value of remarketing.
Do you really need to spend on remarketing? Should you reduce or increase your spend? Incrementality testing will help you understand this. In a recent growth consulting project, I helped a startup identify that a portion of their high-intent audience was already converting without the help of display ads. By shifting focus to cold audiences, they increased new customer acquisition by 25% without increasing the overall ad spend.
Conclusion
Analytics is one version of the truth, Attribution gives you another, but Incrementality gives you the whole truth and should be the "gold-standard" all marketers should aim for.
In today’s fragmented marketing landscape, incrementality testing is crucial for understanding the true impact of your campaigns. It goes beyond the limitations of attribution models like last-click, providing insights that help you allocate your marketing budget effectively, discover underappreciated channels, and ultimately drive more business growth. If your business is still relying solely on attribution models, it’s time to rethink your strategy and embrace the power of incrementality testing.
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