Attribution models: what they are, types and how to tell which channel drives your sales
How to share the credit for each sale among your channels, and why email often comes off worse
An attribution model is the rule that decides how much of the credit for a conversion goes to each channel the customer passed through. It helps you find out which marketing actions really help you sell.
Before buying, a person may see an ad, read a blog post, receive a newsletter and come back through Google. The attribution model splits the value of that sale among those touchpoints.
What is attribution for?
Without an attribution model, each channel seems responsible for everything or for nothing. With one, you can:
Invest better. Find out which channels generate sales and which only bring in visits.
Understand the customer journey. See how many touchpoints the customer needs and in what order.
Avoid undervaluing channels. Some channels rarely close the sale, but they set it up. If you only look at the last click, they seem useless.
It is part of analyzing the customer journey and a basis for calculating the ROI of each action.
Types of attribution models
Imagine a €100 sale. It went through an ad, the newsletter and a Google search, in that order. This is how each attribution model would split it:
| Model | How it splits the credit | Ad | Newsletter | Search |
|---|---|---|---|---|
| Last click | All to the last touchpoint | €0 | €0 | €100 |
| First click | All to the first touchpoint | €100 | €0 | €0 |
| Linear | In equal parts | €33 | €33 | €33 |
| Time decay | More weight to the most recent ones | €15 | €30 | €55 |
| Position-based | 40% to the first, 40% to the last and the rest to the ones in the middle | €40 | €20 | €40 |
| Data-driven | Based on learning from actual conversions | Variable | Variable | Variable |
Rule-based models (the first five) are easy to understand, but none of them is “the right one”. Each one tells the story from a different point of view.
The data-driven model (data-driven attribution) uses your account’s conversion history to estimate how much each touchpoint contributes. It is the most accurate attribution model when there is enough data.
Which models remain in GA4 and Google Ads?
Google simplified attribution in 2023. It removed the first-click, linear, time-decay and position-based models from Google Ads and Google Analytics 4.
Today, in those tools, you can choose between two attribution models:
Data-driven. The default model.
Last click. All the credit goes to the last channel that was clicked.
The other attribution models are still useful as a way of thinking. You can apply them in other tools or in a spreadsheet, but no longer in Google’s.
Do you know how much your emails sell?
Add UTM parameters to your campaigns with Mailrelay and find out which sales start in your newsletter.
How to choose an attribution model
If your sales are quick and impulsive, last click is usually enough: there are few touchpoints before the purchase.
If the sales cycle is long, as in B2B, the data-driven model better reflects the channels that accompany the decision.
If you have few conversions, the data-driven model has less information to learn from. Always compare it with last click.
Whatever the attribution model, keep it stable for a while. If you change it every month, you won’t be able to compare.
Attribution and email marketing
Email is usually in the middle of the journey: it reminds, informs and prompts people to come back. That’s why last click often undervalues it. The customer opens the newsletter, gets interested, and days later buys after arriving from Google.
To measure it properly:
Tag all links with UTM parameters. For example, “utm_source=newsletter”, “utm_medium=email” and “utm_campaign=” with the name of the mailing. That way your analytics knows the visit comes from email.
Look at assisted conversions. In GA4, the conversion path reports show which journeys include email even when it isn’t the last step.
Compare periods with and without mailings. If sales go up on newsletter days, email is contributing.
Common mistakes
Relying only on last click. It penalizes the channels that set up the sale, such as email or content.
Not tagging links. Without UTM parameters, many email visits show up as direct.
Comparing different attribution models. A channel can look worse just because you switched models.
Forgetting what isn’t measured. Referrals, phone calls or visits to the physical store also have an influence.
How Mailrelay helps you
With Mailrelay you can add UTM parameters to the links in your campaigns, see which links get the most clicks and cross-reference that data with your analytics tool. That way you know how much of your sales start with or pass through your emails.
The free account includes up to 80,000 emails a month and 20,000 contacts, with human support by chat, ticket and phone.
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Frequently Asked Questions
These are the most common questions about attribution.
What is an attribution model in a nutshell?
A rule for sharing the credit for a sale among the channels the customer passed through.
What is the best attribution model?
It depends on your business. In GA4 and Google Ads, data-driven is the recommended one if you have enough conversions; last click is simpler to understand.
Why does the linear model no longer appear in Google Analytics?
Google removed it in 2023, along with the first-click, time-decay and position-based models.
What is last-click attribution?
The model that gives all the credit for the conversion to the last channel the customer clicked before buying.
How do I know if my emails generate sales?
Tag your links with UTM parameters and check the direct and assisted conversions of the “email” medium in your analytics.