Google Ads Attribution Models

What is DDA?

You may have received an email from Google recently explaining that the way it measures conversions is about to change. Instead of ‘Last Click’ attribution, it will use ‘Data Driven’ instead. This is the email here:

Email from Google Ads explaining the switch to DDA


Unless you’re a complete search marketing data nerd, this probably doesn’t mean a lot to you, so we’re going to explain. The bottom line, however, is that it’s not going to change very much for your PPC campaign at all.

Let’s start with how Google measures conversions. 

A ‘conversion’ as we define it in 80/20 Digital, is when someone calls up your business or sends an enquiry via an online form. They get recorded in the Google Ads dashboard, and up until now, Google has always used a conversion measurement called ‘Last Click’ to record it. i.e., what was the last ad clicked and last keyword typed into Google that the searcher used to find your business and make an enquiry?

Last Click makes sense. It’s simple. But it does somewhat disregard the other ads that may have contributed to the buyer journey. How so?

Let’s say you wanted to find a buyers advocate to help you purchase a new home. You start off with some high-level searches like “buyers advocate” or “best buyers advocates in Melbourne”. You gather some info about the various providers, but you’re not ready to make a decision yet – you’re still gathering information. 

A few days later, you’re reading the news online, and you see a banner ad for one of those same buyer’s advocates. You click on the banner, and it takes you back to the website for another visit. A few weeks later, you’re ready to make a decision, and because those banner ads have been following you around the internet, you google the advocate’s brand, click on an ad to visit the website and make an enquiry.    

Now, which of those ads was responsible for getting the enquiry? The first, second or third? Or all of them? 

Congratulations. You’ve now entered the world of Attribution.  

Google Ads Attribution Modelling 

Attribution is simply a way of identifying which ad or ads contributed most to the sale you just made. This is a table from Google explaining how it records the different types of attribution available on its Ads platform.

Table explaining Google’s Attribution Models

Google actually has 6 different types of attribution models to help figure out which ads, keywords, and campaigns are actually working hardest to drive enquiries to your business. They are:


⦁ First Click
⦁ Time Decay
⦁ Linear
⦁ Position-based
⦁ Data Driven
⦁ Last Click


There’s a good argument to say that the ad that draws the First Click to your website is actually more important because it introduced your brand to the searcher.

There’s an equally strong argument to say that they all mattered, so we should use Linear Attribution. In this case, Google gives one credit to all three ads from our example, so 0.3 of a conversion each (doesn’t have to be 3, by the way, it can be 5, 10, 20 or however many you want). 

Position-Based Attribution is similar to Linear except 40% of the credit (0.4) goes to the first click, 40% to the last click (0.4) and 20% for all the ads in between. If there is only one ad in the middle, it would get 20% or 0.2. If there were two ads in the middle, they would get 10% (0.1 each) and so forth.

Then there’s Time Decay, where the clicks take on exponentially more importance as the searcher gets closer to making an enquiry within a 7-day window. If it converts on day 8, it only gets 0.5 of a credit. 

Data-Driven Attribution means that Google will figure it all out for you based on the data is has collected in your account to date and give credit to whichever of ads play the biggest role in your conversions.    

In the past, Data-Driven Attribution used to be for big-budget advertisers only. You couldn’t even use it unless you had at least 3,000 ad interactions on supported networks and 300 conversions within 30 days. Basically, that’s an average pf 10 conversions per day to able to use Data-Driven Attribution on a given conversion action.

So why is Google forcing us all to change to Data-Driven Attribution? What if you don’t average that number of conversions per day?

Well, Google says its machine learning algorithms now have the capability to support much smaller data sets and still provide accurate reporting. Secondly – and this is the real point – Data-Driven Attribution will work much better when tracking cookies disappear from Google entirely.

A Cookie-Less Future

All over the world, privacy laws have been tightening and Google is rebuilding its platforms like Google Ads and Google Analytics 4 to function without tracking cookies.

Cooke Monster sitting on a bench saying ‘Without Cookies I’m just a Monster

It’s all part of a much broader trend to protect consumers’ privacy while also providing accurate data to marketers.

What does DDA mean for my Google Ads?

Actually, very little. You will see some decimal points appearing where there have been interactions with multiple ads, which can look a little odd. Compared side by side, this is what it might look like:

Last Click Vs DDA example

For example, it can be a bit hard to get your head around getting 2.5 or 1.5 conversions instead of just 3 or 1, especially if you’re only really interested in measuring phone calls and email enquiries. But basically, all it means is that some ads and keyphrases contributed partly to conversion on the journey to an enquiry.

There is also a rather ominous-looking window after switching that looks like this, which suggests that there may be a temporary dip in conversions, but this should catch up within a few days:

Google Ads timeline of how the switch to DDA affects campaigns

And of course, there is the inevitable prod from Google to increase budgets…. which, of course, we always take with a grain or three of salt.

In other good news, it appears that Google’s DDA model is actually functioning more like Last Click anyway for advertisers spending less than $10k per month. 

In short, it won’t make a big difference to 80/20 clients – your phone will still ring, but the reporting might look a little different.

Want better results for your lead generation campaign? Talk to the Google Ads experts at 80/20 Digital. Call now on 0400 677 202.