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Guide 76 · Attribution · GA4 + Tag Manager

Data-driven attribution in GA4: what the model does, and how to check it is the model in use

Checked 11 November 2026 · Verification: figures recomputed in Python 3, shown in the downloadable file · Steps traced to Google help and developer pages, opened 11 November 2026 · 7-minute read

Data-driven attribution splits credit across touch points using your own converting and non-converting paths. This guide shows where the setting lives and how to read the result.

Expected signal

After the trace, Admin shows the reporting attribution model as Data-driven, and the Advertising reports credit more than one channel for the same purchase.

Download the reference: the data driven attribution reference (JSON) (554 bytes, MD5 cf4dc00b71e0eab7f8611f505de54cbd). It holds the worked example from this guide with every figure recomputed. The file was built for this guide and checked the same day; it was not exported from a live property.

What you need

  • Editor or Marketer access at property level to open Attribution settings.
  • A property with purchase or another key event already collecting.
  • The Advertising section open in a second tab, so you can see the reports the setting feeds.

The trace

  1. Open Admin, then under Data display click Events, then Attribution settings. Google lists this path on the attribution page. You need Marketer access or above at property level to change the setting.
  2. Read the Reporting attribution model field. On a property that has not been changed, it reads Data-driven. That is the default Google ships, and the page calls it the model that uses your account data to work out the actual contribution of each click.
  3. Leave Channels that can receive credit on its default unless you have a written reason to change it. The default credits paid and organic channels. Changing it changes which channels can appear in the reports at all.
  4. Read the Key event lookback window. It sets how far back GA4 looks for touch points to credit. Note the value before you change anything, so a later change can be traced back to this reading.
  5. Check the model against Google's own worked example. Google shows four ad exposures leading to a 3% chance of a key event, and 2% when the fourth exposure is removed. The lift is (3 - 2) / 2 = 50%. That is the counterfactual idea in one line: the model asks what happens when one touch point is taken away.
  6. Now check the split on your own numbers. In the worked example in the download, 120 purchase conversions split 42% to Paid Search, 33% to Organic Search and 25% to Email. That is 50.40, 39.60 and 29.28 credits, and the three add to 120.00. A last-click report would have given all 120 to one channel.

Dead ends

DEAD END — EXPECTING WHOLE NUMBERS. Data-driven credit is fractional. A channel can hold 50.40 conversions. If you round each row to a whole number before adding, the total will not match the property total.

DEAD END — DIRECT GETS CREDIT IT SHOULD NOT. All models exclude direct visits from credit unless the whole path is direct. A path of Paid Search, then Direct, then purchase does not credit Direct.

DEAD END — CHANGING THE MODEL AND EXPECTING OLD REPORTS TO STAY. The reporting model applies to key event reports. Changing it reads the same paths again under the new rule, so past numbers move. Note the date of any change.

End state

The worked example checks out: the fourth exposure lifts the chance from 2% to 3%, a 50% lift, and the 120-conversion split adds to 120.00. The setting is Data-driven, the lookback window is noted, and more than one channel holds credit for the same purchases.

Sources

Checked 11 November 2026. The click paths above are the ones in Google's help and developer pages, opened 11 November 2026. No step in this guide was run inside a live Analytics property or a live Tag Manager container, because both need a Google sign-in and this site does not sign in as anyone. The figures on this page were recomputed in Python 3 and are shown in the downloadable file, which was checked the same day. Google moves menu items without warning; if a path on this page no longer matches, the linked help page is the current map.