Understanding attribution can be a daunting task for any ecommerce marketer, especially if you're trying to make sense of it all without the support of an experienced ecommerce marketing agency. 

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A while back we wrote a post on the ins and outs of the Meta pixel and how the platform attributes sales back to it’s campaigns. 

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Now we’re talking about Google, and the various attribution models on offer to accurately assign credit for your purchases from Google. 

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What is an attribution model? 

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In simple terms, an attribution model determines how credit for a conversion (like an add-to-cart or a sale) is assigned across your campaigns. Depending on the model, different touch points get more (or less) of the glory.

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So, what options does Google offer?

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There are currently six main attribution models in Google Ads:

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First-Click

Last-Click

Position-Based

Linear

Time Decay

Data-Driven

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Now let’s break them down one-by-one, looking at the pros and cons of each model and which one is most suitable for your ecommerce brand. 

1. First Click Attribution

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Overview:

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This model gives 100% of the credit for a conversion to the first interaction a user had with your ad. It's ideal for understanding what sparked initial interest, especially in long, multi-touch journeys.

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Pros:

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- Great for brands focused on upper-funnel activity and building awareness.

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- Helps surface channels or keywords driving initial engagement.

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Cons:
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- Ignores the impact of later touchpoints, even if they played a key role in the conversion.
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- Can distort performance reporting if most conversions happen further down the funnel.

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Best for:

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Brands with longer buyer journeys prioritising brand discovery and top-of-funnel investment.

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2. Last Click Attribution

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Overview:

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All conversion credit goes to the final interaction before the user took action. This model focuses on what closed the deal.

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Pros:‍

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- Simple and commonly understood.
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- Useful for brands optimising bottom-of-funnel tactics.

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Cons:

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- Completely ignores upper-funnel influence.
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- Risks under-investing in awareness and consideration channels.

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Best for:

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Short sales cycles, or when you're laser-focused on performance and immediate ROI.

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3. Position-Based Attribution

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Overview:

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Also known as the U-shaped model, this gives 40% of the credit to the first and last click each, with the remaining 20% spread across the middle touchpoints.

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Pros:
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- Balances both the spark of interest and the final push.
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- Ideal for multi-touch journeys where both awareness and closing matter.

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Cons:

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- Still somewhat arbitrary – assumes the middle touches matter less.
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- Doesn’t adapt based on real data or customer behaviour.

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Best for:

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Brands wanting a more blended and balanced attribution without jumping into machine learning.

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4. Linear Attribution

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Overview:

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Spreads credit evenly across all touchpoints leading to a conversion. Every step in the customer journey is treated equally.

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Pros:

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- Encourages more holistic optimisation across the full funnel.
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- Good for brands with consistent engagement across all stages.

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Cons:

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- Over-values weaker touchpoints if the journey has many steps.
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- Doesn’t prioritise what's actually most influential.

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Best for:

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Journeys that are consistently complex and involve multiple touchpoints of roughly equal value.

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5. Time Decay Attribution

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Overview:

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Distributes credit exponentially - more is given to interactions closer to the conversion, with earlier touchpoints receiving less.

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Pros:

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- A good fit for longer journeys where recency is key.
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- Fairer than Last Click, as it still gives some credit to upper-funnel efforts.

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Cons:

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- Can undervalue awareness campaigns which are essential for initial interest.
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- Makes sense only if touchpoints really lose value over time.

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Best for:

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Businesses with longer sales cycles where final interactions are clearly more impactful.

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6. Data-Driven Attribution (DDA)

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Overview:

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This is Google’s preferred and default attribution model - It sses Google’s machine learning to analyse account-specific data and assign credit based on actual conversion behaviour. It’s dynamic and adapts to what truly works.

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Pros:
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- Tailored to your real customer insights – no assumptions.

- Best at optimising budget based on true impact.

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Cons:
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- Requires sufficient conversion volume to function.
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- May be overkill for smaller advertisers with limited data.

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Best for:

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High-volume advertisers wanting the most accurate view of what’s driving real value.

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Conclusion

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Attribution isn’t glamorous, but it’s one of the hidden levers behind profitable ecommerce growth.

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For brands generating a solid volume of conversions through Google Ads (think 30–40+ a month), Data-Driven Attribution is usually the strongest choice - but even then, it’s only as good as how you use it.

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Whether you're nurturing new customers or wringing more efficiency out of existing campaigns, the attribution model you choose has a massive influence on where your budget goes - and what gets quietly cut.

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As a digital marketing agency for ecommerce brands, we know the nuances of each model across all major ad platforms, and we can help you pinpoint the approach that gives your brand the clearest path to scalable growth.

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