Attribution analytics: five questions your data must answer
The five questions are which channels start journeys, how long buyers take, how many touches they need, how many are new, and how much traffic is unassigned. GA4's attribution paths report and Shopify's customer reports answer them from data you already have.
By Joris van Huët, Founder & CEOPublished 5 min read
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Ask five questions before you buy a tool: which channels start journeys, how long buyers take, how many touches they need, how many buyers are new, and how much traffic has no channel. GA4's attribution paths report answers the first three, and it displays paths up to 20 touchpoints long. Shopify and GA4's channel groups answer the other two. The five describe what happened, not what the spend caused.
Which channels start journeys, and which finish them?
Open Advertising in GA4 and find the attribution paths report (Google's help page calls it the key event attribution paths report), then pick your purchase key event at the top left. The chart shows which channels initiate, assist and close key events, split into early, mid and late touchpoints: early is the first 25% of touchpoints in a path, late is the last 25%. The table breaks paths out by primary channel group, and its dropdowns switch to source, medium or campaign.
Last-click credits only the final touchpoint, so a channel that appears mostly early gets little or nothing in a last-click report. Google's attribution models also leave direct visits out of the credit unless a path is made only of direct visits. If many of your paths look like that, check tagging before you read anything into the channel.
How long do buyers take, and through how many touches?
The same table carries days to key event and touchpoints to key event for each path, and you can filter by path length to isolate single-touch buyers. Attribution tools stop counting somewhere, so the days matter. GA4's key event lookback window defaults to 30 days for first_visit and first_open and 90 days for other key events, and ad platforms apply their own windows, such as the conversion window in Google Ads. Shopify's marketing reports reset the first interaction after 30 days without a purchase, so its journeys and GA4's can differ for slow buyers. A buyer who takes longer than a window is invisible to that window.
How many buyers are new, and how much traffic is unassigned?
Use Shopify for new buyers. Its New vs returning customers report displays the number of first-time and returning customers for a given period. GA4's new users metric counts something different: new unique user IDs that logged first_visit or first_open, so a returning buyer who arrives under a new ID counts as new there.
For the unassigned share, open Reports, Acquisition, Traffic acquisition and read the channel group column. Google defines Unassigned as the value Analytics uses when no channel rule matches the event data, which happens with user-defined sources or mediums and with missing session information.
How do you check the five answers against your own store?
Fill in this sheet from the last full month:
- Start and finish. The channels that dominate early and late touchpoints for your purchase key event.
- Days. Days to key event, next to each ad platform's click window.
- Touches. Touchpoints to key event, and the share of single-touch paths.
- New. The first-time share from Shopify's New vs returning customers report.
- Unassigned. Unassigned sessions divided by total sessions.
Pass: the paths report's total key events differ from Shopify's orders for the same dates by a gap you can explain (refunds, cancellations, time zones, buyers who declined tracking), and you can name the source and medium behind each Unassigned row. Fail: the gap is unexplained, or most paths are Direct-only or (not set). Fix tagging first; until the gap is explained, the numbers aren't ready to carry a budget decision.
What do these five answers not tell you?
They describe what happened, and credit along a path is not what would have happened without the spend. Gordon and colleagues compared 15 US advertising experiments at Facebook, with 500 million user-experiment observations and 1.6 billion ad impressions, against observational models, and report that the observational methods often failed to produce the same effects as the randomised experiments, even after conditioning on extensive demographic and behavioural variables (Marketing Science, 2019). That covers Facebook ads, not every channel, so read it as a caution about treating paths as causes, not as a verdict on GA4. A holdout test or a causal read is the next step, and the five answers tell you where to point it.
Sources, 30 September 2026: Key events attribution paths report (Google, Analytics Help); Get started with attribution (Google, Analytics Help); Select attribution settings (Google, Analytics Help); Default channel group (Google, Analytics Help); Tagging best practices to avoid unassigned traffic (Google, Analytics Help); Dimensions and metrics (Google, Analytics Help); URL builders (Google, Analytics Help); About conversion windows (Google, Google Ads Help); Customers reports (Shopify Help Center); Marketing reports (Shopify Help Center); A Comparison of Approaches to Advertising Measurement (Gordon, Zettelmeyer, Bhargava and Chapsky, Marketing Science, 2019, peer-reviewed).
Related answers
Frequently asked questions
Where is the attribution paths report in GA4?
In GA4, click Advertising on the left and open the attribution paths report, which Google's help page calls Key events attribution paths. Pick your purchase key event at the top left. The table shows key events, purchase revenue, days to key event and touchpoints to key event, broken out by channel group.Why does GA4 show some of my traffic as Unassigned?
GA4 labels traffic Unassigned when no channel rule matches the event data, for example a user-defined medium or missing source information. Open the row, add source and medium as a second dimension, and fix the tags behind the biggest entries first.Does GA4 count a returning buyer as new?
It can. GA4's new users metric counts new unique user IDs that logged first_visit or first_open, not first-time buyers. Shopify's New vs returning customers report counts first-time and returning customers from orders, so use it for the buyer question.
Go deeper: Incrementality testing, explained.
Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.
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Terms in this article
- Ad ImpressionAd Impression is a single instance of an advertisement displaying on a webpage. Impressions are a key input for models measuring the causal impact of ad exposure on user behavior.
- AttributionAttribution identifies user actions that contribute to a desired outcome and assigns value to each. It reveals which marketing touchpoints drive conversions.
- Attribution ModelAn Attribution Model defines how credit for conversions is assigned to marketing touchpoints. It dictates how marketing channels receive credit for sales.
- Causal AttributionCausal Attribution uses causal inference to determine which marketing touchpoints genuinely cause conversions, not just correlate with them.
- Conversion PathConversion Path is the sequence of interactions a user has with various touchpoints before completing a desired action.
- Facebook AdsFacebook Ads are paid advertisements appearing on Facebook and Instagram. Businesses use them to target specific audiences based on demographics and interests.
- Holdout TestA holdout test is an experiment where a portion of the audience does not see a campaign. This measures the campaign's true incremental impact.
- Multi-Touch AttributionMulti-Touch Attribution assigns credit to multiple marketing touchpoints across the customer journey. It provides a comprehensive view of channel impact on conversions.