Answering the question "what is incrementality" is a bit like trying to define the word "warm." It depends on who you’re asking. According to 5W’s PR Advantage in Affiliate Marketing 2026 report, last-click attribution systematically over-credits coupon and cashback affiliates and under-credits content partners, which is exactly why brands can’t treat every affiliate-attributed sale as equally valuable. Just as a person raised in Minnesota is likely to have a different perspective on what it means to be warm than a person raised in Singapore, one brand will have a different point of view about incrementality than another brand.
Instead of understanding incrementality as a term with a rigid definition, it’s far more useful to perceive it as a concept. The concept of incrementality is as follows:
- The ability to directly tie spend (or some other input) to a specific outcome, in an effort to identify the effectiveness of a marketing channel, a partner, and/or optimization tactic.
- The process of identifying specific interactions that propel consumers from a passive state to an active state in any given desired action.
- A way to measure an event that wouldn’t have occurred unless a certain action or interaction was taken.
Key Takeaways
- Incrementality is a concept, not a fixed formula. What counts as "incremental" is unique to each brand’s goals.
- Last-click attribution tends to over-credit coupon and cashback affiliates while under-crediting content partners that introduce new customers earlier in the journey.
- Defining incrementality starts with asking the right questions about what action you actually want your affiliate partners to drive.
- Brands that explicitly define and measure incrementality can renegotiate partner cost structures, cut non-incremental spend, and reallocate budget toward the partners actually driving growth.
Incrementality means something different to every brand
How brands define incrementality varies; every program arrives at its own definition based on what it’s actually trying to achieve. eMarketer’s 2026 outlook on affiliate marketing notes that as AI-driven discovery reshapes how consumers find brands, attribution itself is getting harder to pin down, which makes a brand’s own definition of incrementality even more important than the attribution model alone. This is because a "desired outcome" is different from one brand to the next. Each affiliate partner contributes to a piece of the marketing pie, so a brand’s specific definition of incrementality shapes which partners get credit, which get cut, and which get more budget.
Common ways brands measure incremental value
Some actions that brands may look at within their affiliate program to assess incrementality include:
- Increase in new customer acquisition
- New products purchased that had not previously been purchased by that customer
- Basket size increases
- Orders that had no other channel or partner involved in the conversion path
- New email signups
- Increased brand exposure from a specific channel
- Increase in leads within a purchase funnel
- Increase in sale-active partners in a revenue-driving program
- New-to-channel revenue driven through optimization efforts
- Increase in projected key performance indicators (KPIs) as a direct result from the affiliate program
- Increased adoption and sales of additional product lines or business units
- Increase in traffic tied back to affiliate promotions and activities
These are just a few ways brands evaluate incremental actions within their programs. The key point is that it’s ultimately up to the brand to determine what action or actions they deem incremental. Once that’s decided, that definition can be used to set incrementality goals, track efforts, allocate spend toward those actions, and even reduce spend in areas that don’t meet that criteria.
How can I determine what incrementality means for my affiliate program?
Establishing what incrementality means for your affiliate program starts with asking the right questions. Here are a few we ask our clients to help them define incrementality for their affiliate program:
- How is incrementality defined by your company?
- What is the desired action you want your affiliate partners to deliver?
- Are there specific partner types (e.g. content, loyalty, coupon) that you feel are driving more or less incremental value to your program right now? If yes, why?
- Are you viewing incrementality at a macro or micro level for your business?
- What metrics or variables are considered most important to your affiliate program?
- Have you performed any incrementality testing internally before? If yes, what were the results and learnings?
- How are you achieving desired incrementality in other channels, like paid marketing or email? How does your brand track this incremental revenue internally?
- How would you define your current customer?
- What is the typical purchase cycle you see for your product or products?
- At which point in the purchase path do you see the highest cart abandonment rate?
Every brand will have its own unique perspective on and answers to these questions, based on what they value and what their data shows, whether that’s provided by their affiliate network or SaaS platform, or gathered internally. Once your team has enough perspective and data to answer some of these questions, you’ll be able to establish a performance baseline by channel and by partner vertical, such as content, loyalty, mass media, coupon, brand-to-brand, or mobile. From there, all partner activities and initiatives can be centered around maintaining or improving those incremental KPIs, and perhaps even optimizing away from partners who don’t meet those standards.
What does putting an incrementality definition into practice actually look like?
When Leesa returned to Acceleration Partners after a stint with a smaller, more cost-effective agency, their affiliate program’s revenue base and return on ad spend (ROAS) had both declined. The Acceleration Partners team completed a full program audit, recommended moving the program back to last-click attribution, and implemented creative optimizations with top mattress review sites and content partners. The relaunch drove a 200%+ ROAS increase, a 7.6% month-over-month traffic increase, and 2% added revenue month-over-month. The lesson generalizes well beyond mattresses: an attribution model and partner mix that don’t match how a brand actually wants to define incrementality will quietly understate, or overstate, what’s working.
Meaningful marketing
Too often, brands claim that their affiliate partners aren’t driving incremental value, when the real issue is simpler: those affiliate partners don’t have a clear understanding of what the brand’s definition of incrementality is or how it’s being measured and evaluated. This missing information makes it difficult for them and the program management team to support those outcomes.
Some brands also perceive certain partner types, like content, coupon, or loyalty, to be more incremental than others, which may or may not be accurate. It all comes back to what the brand’s unique definition of incrementality is for their affiliate program and their business. Each affiliate partner contributes to a piece of the marketing pie, so it’s important to maintain a healthy balance of partners within your affiliate program, since each can add value in their own way. This balanced approach also helps reduce program contribution risk and maintain healthy sales from different audience groups driven by the portfolio of partners in a program.
It’s necessary to communicate incrementality goals to your affiliate partners so they understand why certain decisions are made, and what success looks like for both themselves and the brands they’re working with. With better alignment, open communication, and clear objectives, even when business goals shift, brands will realize better incrementality across their affiliate program and every other marketing channel they operate.
Frequently asked questions
Is incrementality the same thing as attribution?
No. Attribution is a transaction-level analysis that models the impact of multiple marketing touchpoints on a given sale. Incrementality looks at the people behind those transactions and measures whether their behavior actually changed because a marketing channel was present. Understanding incrementality can help you build a more accurate attribution model, but the two measure different things.
Which affiliate partner types tend to be the most incremental?
It varies by brand and category, but content partners, reviewers, and creators that introduce a customer to a brand earlier in the funnel are generally considered more incremental than partners that capture a sale right at the point of purchase, like coupon or cashback sites operating on branded search. That said, coupon and loyalty partners can absolutely drive incremental value when they’re recruited and managed with that specific goal in mind, rather than left to capture sales that were already going to happen regardless.
How long does it take to see results after redefining incrementality for a program?
It depends on the brand and the scale of the change, but meaningful shifts can happen within a few months. Acceleration Partners helped a large mattress retailer build a custom incrementality dashboard and optimize and renegotiate partner cost structures within three months of the engagement starting, making the program both more cost-effective and better aligned with the client’s specific incremental KPIs.
Do small or newer affiliate programs need to worry about incrementality?
Yes, even more so than mature programs in some ways. Smaller programs have less room to waste budget on non-incremental spend, and building a clear incrementality definition early prevents the program from scaling around the wrong partner mix. It’s easier to set a performance baseline correctly from the start than to untangle years of last-click attribution later.
What’s the first step to start measuring incrementality?
Start by deciding what "incremental" actually means for your brand: is it new customer acquisition, basket size increases, new-to-channel revenue, or something else specific to your business? From there, work with your affiliate network or program management team to set a performance baseline by partner type so you have something concrete to measure improvement against.
Ready to take your affiliate program to the next level? Connect with our team of affiliate marketing experts today, and learn how to effectively define incrementality for your program.
