CarrTalk: The Challenges of Advertising Incrementality

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Marketplace advertising has entered a new era.

Amazon and Walmart are no longer platforms where brands can rely on organic visibility alone. Advertising has become a structural requirement for growth. But as ad budgets expand year after year, a more important question has surfaced:

Are those dollars actually creating new growth, or simply taxing existing demand?

In a recent CarrTalk discussion, Owen Carr, Chief Merchandising Officer at Spreetail, sat down with Chief Marketing Officer, Amit Dodeja, to unpack one of the most misunderstood topics in ecommerce today: advertising incrementality.

The Marketplace Has Shifted — Permanently

To understand why incrementality matters, you first have to understand how dramatically the marketplace landscape has changed.

In Q4 alone, Amazon delivered 13 billion items same day globally (a 70% year-over-year increase). That operational acceleration is reshaping consumer expectations and competitive dynamics.

Owen explains:

“For every day of improved shipping speed, a brand can see 8 to 12% increase sales velocity — and that’s just direct additional customers versus the competition.”

When delivery speeds improve, algorithms prioritize those listings, helping brands compete more effectively for the Amazon Buy Box. Faster omnichannel ecommerce fulfillment increases conversion rates across marketplaces. Late holiday cutoffs extend buying windows. Operational excellence translates directly into sales velocity.

At the same time, advertising growth is accelerating at scale:

• Amazon advertising grew 18%
• Walmart advertising grew 27%

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These are not incremental gains on small bases, they represent billions in additional spend flowing into marketplace ecosystems.

“There’s really less organic surface area on the sites now and ads are really the game in town,” Owen notes.

In other words: marketplace growth has become pay-to-play. But simply participating in the ad auction doesn’t guarantee you’re creating new demand.

Wasted Spend Is Common

One of the most eye-opening parts of the discussion centers around how much ad spend may be non-incremental.

Amit shares:

“When we started this journey, we realized maybe 50% of our ad spend was potentially being wasted.”

That estimate came from a brand that was already paying attention and investing in analytics. For brands without that discipline, the percentage may be even higher.

Non-incremental spend often hides in:

• Branded keyword campaigns that capture customers already searching for you

• Overbidding on high-organic-rank SKUs

• Poor campaign structure

• Duplicate targeting

• Inefficient SKU-level attribution

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“If you’re not thinking about incrementality as at least your top two to three priorities,” Amit says, “you’re probably burning money and eating into your profit.”

The financial impact compounds quickly. On a $10M annual ad budget, even 30% inefficiency represents $3M in wasted capital.

Why Measuring Marketing Incrementality is Difficult

If incrementality is so important, why don’t more brands master it? Because it’s structurally hard.

Marketplace ecosystems are dynamic:

• Competitors change bids daily

• Categories fluctuate seasonally

• New entrants disrupt pricing

• Algorithms update constantly

• Shipping speeds influence ranking

• Promotions alter conversion behavior

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A campaign that is incremental today may not be incremental next month. Additionally, many brands oversimplify performance measurement.

Owen observes:

“Brand owners will try and boil their ads down to one thing — like ROAS or spend. That’s very dangerous.”

Reducing advertising to a single KPI is like judging an entire business by one financial metric. It ignores context, interaction effects, and long-term impact.

Amit adds:

“Incrementality is more of a triangulation game. You have to pull data from a bunch of different sources. You have to piece the story together.”

That triangulation often includes:

• Organic ranking shifts

• Share-of-voice data

• Keyword-level performance

• SKU-level attribution

• Traffic flow between variations

• Market share changes over time

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This cannot be managed effectively with spreadsheets alone. It requires structure, systems, and ongoing analysis.

Practical Ways Brands Can Test Their Advertising

Fix the Foundations

Before optimizing, brands must assess structural discipline:

• Are campaigns built around single ASINs or grouped inefficiently?

• Is there clarity between branded and non-branded targeting?

• What percentage of revenue is reinvested in ads?

• Is spend aligned to growth objectives?

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Without clean architecture, measurement becomes unreliable.

As Amit describes it:

“You have to have the right form before you can actually do that rep — before you swing that club.”

Run Controlled Experiments

The fastest way to reveal incrementality is uncomfortable but effective:

“The easiest way to answer that question is… go dark.”

Pausing ads temporarily, strategically, and carefully reveals how much organic demand sustains without paid support. Brands unwilling to test may already sense the answer.

Build Infrastructure

True incrementality measurement requires investment in data systems that integrate:

• Paid signals

• Organic signals

• Competitive movement

• Product-level attribution

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Without that infrastructure, brands default back to platform-reported metrics — which only tell part of the story.

Full-Stack Marketing: Beyond PPC

Incrementality also extends beyond sponsored product ads. Once bottom-of-funnel demand is captured, brands must stimulate new demand through:

• DSP campaigns

• Influencer marketing

• Publisher partnerships

• Strategic promotions

• Pricing adjustments

• SKU launches

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“If you’ve captured all the demand at the bottom of the funnel,” Amit explains, “then think about DSP to generate more demand… lean on influencers… be full-stack marketers.”

Marketplace growth requires coordinated ecommerce services across operations, promotions, fulfillment, and advertising. Isolated optimization is no longer enough; brands need omnichannel ecommerce solutions that connect advertising, fulfillment, pricing, and marketplace execution.

Final Takeaway: Growth Demands Discipline

The brands that will win over the next decade aren’t the ones spending the most. They’re the ones proving their spend is incremental.

Incrementality forces discipline. It forces brands to move beyond vanity metrics like ROAS and clicks. It forces them to question platform-reported performance. It forces them to test, triangulate data, invest in infrastructure, and think beyond PPC into full-stack demand generation.

As Amit put it, the question is simple: “Did the sale happen because of the ad, or would it have happened anyway?”

If brands cannot answer that confidently, they are likely subsidizing revenue they already owned.

True marketplace growth requires a stronger ecommerce growth strategy — from optimizing ads to optimizing market share. From chasing efficiency metrics to building systems. From spending more to spending smarter.