Business Case for Implementing "Always-On" Incrementality Testing in a Marketing Team

1. Introduction to Incrementality Testing

Incrementality testing is a method used to determine whether a specific marketing tactic (e.g., paid ads, direct mail, or new channel investments) truly drives additional revenue or conversions beyond what would have happened without the marketing intervention. Typically, it involves establishing control groups (who do not see a particular campaign or ad type) and comparing their behaviour to test groups (who do see those marketing tactics).

By continuously running these experiments—often referred to as an "always-on" approach—marketing teams gain real-time insights into the effectiveness of their activities. They can make data-driven decisions to optimise spend, channel mix, and creative strategies.

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2. Key Benefits of Always-On Incrementality Testing

• Precise Revenue Attribution
  
  • ASOS (Fashion E-commerce) adopted an "always-on" testing culture and saw a ~24% YoY revenue growth (reaching nearly £2 billion). A single geo-experiment also yielded a 22% lift in site visits and sales—equating to approximately 360,000 new potential customers.
    (Source: Think with Google)‍
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  • Faherty (DTC Clothing Brand) used cross-channel incrementality tests to align budgets with channels that genuinely drove revenue, resulting in a 53% increase in sales and a 33% growth in new customers within one year.
    (Source: Upwork.com / Measured)
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• Optimisation of Marketing Spend
  
  • Royal Bank of Canada (Financial Services) discovered via incrementality experiments that it was under-investing in key digital channels. By increasing spending by ~200% in test regions, RBC boosted new account openings by over 10% while maintaining cost-per-account targets.
    (Source: Skai.io (RBC Case Study)
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• Identification of High-Impact Channels
  
  • By adding print catalogues to its email-only strategy, the luxury Jewelry E-tailer saw a 28–49% sales lift and a 77–125% lift in inquiries. The campaign yielded a ~600% ROI, translating to about $5 million in incremental annual profit (a 40% profit boost).
    (Source: Harvard Business Review / WhatTheyThink)
    
    ‍Incrementality testing uncovers which channels (e.g., social ads, paid search, print media) are most effective at driving new revenue vs. merely shifting existing consumer behaviour.
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• Accelerated Growth and Competitive Advantage
  
  • Forrester Research shows that when brands systematically measure incrementality, they can boost overall marketing ROI by ~30%.
    (Source: Hunchads.com / Forrester Study)
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• Agility and Continuous Improvement
  
  • It's always been the case that running experiments is best practice. How marketers run best practice experiments has changed as privacy restrictions and last-click and attribution metrics have degraded in quality.
    
    • An HBS study of 35,262 startups found that those using A/B testing and incrementality experiments improved performance by 30%–100% in one year, gaining a substantial edge in user and revenue growth.
      (Source: HBS.edu)

Continuous or "always-on" incrementality testing provides an ongoing feedback loop, enabling real-time pivots. If a campaign underperforms, budgets and tactics can be adjusted immediately, rather than waiting for a quarterly or annual review.

This iterative approach fosters a test-and-learn culture, encourages experimentation, and ensures that marketing strategies remain aligned with consumer behaviour and market shifts.
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Bimodal's clients consistently see a 10-20% increase in marketing efficiency when adopting an always-on approach to marketing science. Additionally, the average media spend of clients has increased YOY while maintaining or improving the efficiency leading to even more revenue.

3. Conclusion

‍Always-on incrementality testing is not just a measurement exercise; it's a strategic approach to ensure every marketing dollar spent contributes actual, additional value. By continuously running controlled experiments, organisations can:

• Validate which channels and tactics drive real lift
• Optimise budget allocation to the most impactful strategies
• Drive sustained revenue growth through data-driven decisions

The experiences of companies like ASOS, Faherty, and RBC and robust research from Harvard Business School and Forrester demonstrate that incrementality testing is a key driver of improved ROI, accelerated growth, and stronger competitive positioning. Adopting this practice allows marketing teams to adapt to an ever-changing landscape swiftly and confidently invest in tactics that genuinely move the needle on business outcomes.