Success in Search Engine Advertising (SEA) isn’t measured by clicks alone, but by the real value it creates. For companies like a.s.r., operating in a dynamic and competitive market, it is crucial to not only increase visibility, but also generate real added value. Incrementality plays a key role here: How can they really know whether a campaign contributes to additional growth? Is a rise in conversion a direct result of SEA, or would that increase have occurred without paid ads as well?  These are questions many businesses struggle with. By taking a critical look at incrementality and applying the right methodologies, businesses can make better-informed decisions and allocate their marketing budgets more effectively.

Together with dentsu, a.s.r. set up a strategic project to better understand and optimise incrementality within their SEA campaigns.

How to measure incrementality: methods and challenges

Measuring incrementality within SEA is complex and requires a thoughtful approach. The complexity of SEA campaigns increases due to the diversity of channels, changing consumer behaviour, and the overlap between organic and paid traffic. While Google now offers solutions to test incrementality, these experiments require a large amount of data just to participate. Because these tests are carried out within a short timeframe, the thresholds are high. Since these thresholds were out of reach for a.s.r., this method was not a viable option.

Other common analytical methods, such as Marketing Mix Modeling (MMM), are time-intensive and require a long implementation period before delivering actionable insights. This meant dentsu and a.s.r. had to find a feasible and effective way to measure incrementality themselves. A collaboration between a corporate like a.s.r. and a specialised marketing agency like dentsu creates unique opportunities here. By leveraging each other’s strengths, they applied innovative methodologies and generated valuable insights.

GEO Experiment with Cronbach’s Alpha

It is expected that not 100% of paid traffic will shift to organic results when paid ads are paused. The goal is to know precisely what percentage of traffic and conversion is lost during the experiment. That’s the incremental value.

• Research question: What is the effect of switching off paid search activities on the total traffic and conversions generated through Search?
• Hypothesis: Once paid search is stopped in the experiment group, organic traffic and conversions in that specific region are expected to increase.

In this case, incrementality was calculated based on a GEO experiment. One region was selected as a control group to capture seasonal variations, while another was chosen as the experiment group, where SEA ads were paused. The question then becomes: how were these specific regions chosen? The selection was based on Cronbach’s Alpha, a statistical method used to analyse how regions behave over weeks or months. Cronbach’s Alpha helps identify regions with similar behavioural patterns, producing a score between 0 and 1. 

Challenges in obtaining significant results

One of the biggest challenges in this project was obtaining significant results, especially at the conversion level. While the impact on clicks became clear relatively quickly, it took longer to gain reliable insights on conversions. The test was therefore extended to allow more data collection, but even with the longer period, the results for conversions remained statistically insignificant. To still draw valuable conclusions, the available data had to be used strategically. The a.s.r. purchase funnel has five steps, allowing the team to examine incrementality not just at the final conversion, but at every stage of the funnel. By analysing where drop-offs occurred in each phase, a solid estimate of the overall impact of SEA on conversions could be made.

Results

By testing incrementality, a.s.r. was able to better grasp SEA effectiveness and use those insights to refine its strategies. The key lesson learned is that incrementality is a continuous process. By combining dentsu’s expertise with a.s.r.’s market knowledge and critically analysing every result, SEA campaigns can be optimised to deliver maximum growth and return on marketing investment.

• The incrementality on conversions was very high, showing that campaigns contributed significantly to additional revenue and growth.
• The incrementality on clicks was lower, meaning that ads mainly shifted traffic rather than generating extra value.

The discrepancy comes from the fact that organic search may capture traffic, but it does not convert as effectively. SEA campaigns direct users to conversion-focused landing pages, whereas organic search typically leads to more informational pages.

Conclusion

This project demonstrates that by critically analysing the impact of SEA, companies can refine their marketing strategies and allocate budgets more efficiently. Want to maximise the value of your SEA campaigns as well? Contact dentsu and discover how a strategic partnership can take your business further.

Testimonial

"Together with dentsu, a.s.r. conducted an experiment within SEA to better understand the incrementality of our campaigns. I experienced the collaboration as very positive. Dentsu’s expertise and insights helped us make our campaigns more effective and impactful. Thanks to their strategic approach and data-driven methodology, we gained valuable learnings that contribute to a more effective use of our marketing budget. A pleasant and professional collaboration that I can definitely recommend!" —  Nienke Schrijver (Online Marketeer at a.s.r. verzekeringen)