Which Attribution Model Should I Use in Google Ads?

An attribution model decides which ad click gets the credit for a sale. People often click your ads more than once before they buy. The model splits the sale between those clicks.

Google Ads has 2 models left. Last click gives all the credit to the last ad clicked. Data-driven shares the credit between the clicks, based on your own account's data. Google dropped first click, linear, time decay and position-based. Any conversion action that used one of those was moved to data-driven.

Data-driven is the default for most conversion actions, and it is the one to keep on a store account. Last click hides the early clicks. Say someone clicks a broad ad for "linen shirts", then comes back a week later through your brand name and buys. Last click gives all the credit to the brand click. So the broad campaign looks like it never sells, and you cut the ad that started the sale.

What if your store is small? Data-driven works at any size. Google says every conversion action can use it, whatever the volume. It works best with at least 200 conversions and 2,000 ad interactions in 30 days. With little data, Google says the two models can give the same result. So you lose nothing by keeping data-driven.

The one fair reason to pick last click is that it is simpler to read. Each sale sits on one click you can point at. If that matters more to you than the full path, it is a fine choice. Just do not switch back and forth, because every switch moves the numbers.

Changing the model changes your numbers, even when nothing else changed. Google lists three things to expect.

First, decimals. Data-driven splits one sale between clicks, so you now see conversions like 0.4 or 2.6. That is normal.

Second, a dip in the last few days. Google Ads puts a sale on the day of the click, not the day of the sale. Shared credit lands on older clicks too, so the newest days look low for a while. Google says to wait until the average days to conversion have passed before you judge. You find that number in the Path metrics attribution report.

Third, credit moves. Some campaigns gain conversions and some lose them, though your sales did not change.

That last one is the dangerous part if you use Target ROAS or Target CPA. Your targets were set on the old numbers. Google says to update them, or the switch can make you overbid on some campaigns and underbid on others. The new model only changes your numbers from the switch onward. To see your past data under the new model, add the "current model" columns, like "Conv. value / cost (current model)".

Here is how. Pick a date range that ends about 2 weeks before the switch, so late sales are in. Compare "Conv. value / cost" with "Conv. value / cost (current model)" for each campaign. Move each Target ROAS by the same percent. Say a campaign's ROAS reads 3.00 the old way and 3.30 under the new model. That is 10% higher, so a 4.00 target becomes 4.40. Those numbers are made up to show the sum.

Run the 5 checks before you switch models. They are free, and a small account takes about an afternoon.

To see where the credit lands, Scaley Media Buyer ($99/mo for all your stores + 1% of total ad spend) reads it for you. It is ours, so keep that in mind as you read. It connects to Google Ads read-only and reads your live campaign, product and search term data. You ask "which campaigns got the credit for my sales this month?" and it answers from the account. It never changes a setting and never runs on its own.

Be clear on what it does not cover. Your tracking tag, your conversion settings, your Shopify orders and your Meta ads are not part of the campaign, product and search term data it reads. So the 5 checks above stay with you.

Scaley has two other levels. Scaley Consultant ($99/mo flat, for all your stores) answers from screenshots and CSVs you upload and connects to nothing. Scaley Suite ($199/mo for all your stores + 4% of total ad spend) finds dead search terms and products every day and queues each one to cut, with the reason, and shows spend and ROAS in one dashboard. Only Scaley Suite writes to an account, and only after your yes on each change. Every level starts with a 3-day free trial, card required.

If the tag was never set up right and you want people to fix it and run the account, ZenoX Media is our ecommerce Google Ads agency, and its team can take that on.