Beyond Last-Click: Which AdWords Attribution Model Is Right For You?

Nineteenth-century department store mogul John Wanamaker is credited with having expressed the now-cliché conundrum in advertising: “Half the money I spend on advertising is wasted; the trouble is I don’t know which half.” These days, with direct-response advertising and sophisticated web analytics, this problem is increasingly one of the past. But as a digital ad campaign manager it can easily be reiterated if you allow yourself to be told only part of the story behind your conversions by defaulting to “last click” attribution in your reporting.

For years, PPC managers have been using last-click attribution as the default attribution model within their accounts, assigning credit for conversions to the last interaction out of oftentimes more than one. When you have an account structure containing keywords that correspond to different points of a conversion funnel, this attribution model can overstate the contribution of a lower-funnel keyword. If you’re using last-click attribution while bidding on the advertiser’s own branded terms, for example, these could be siphoning credit away from the upper-funnel keywords that you’re bidding on, making it look like these are the only ones converting well. And this doesn’t make you look good to your client who is already skeptical of bidding on her own brand’s terms (the reasons for which, as a side note, are well documented).

So what are the other options? For the purposes of this post, I’ll just stick to the attribution models available natively in AdWords:

Last click Last click: Gives all credit for the conversion to the last-clicked ad and corresponding keyword.

First click First click: Gives all credit for the conversion to the first-clicked ad and corresponding keyword.

Linear Linear: Distributes the credit for the conversion equally across all clicks on the path.

Time decay Time decay: Gives more credit to clicks that happened closer in time to the conversion. Credit is distributed using a 7-day half-life. In other words, a click 8 days before a conversion gets half as much credit as a click 1 day before a conversion.

Position-based Position-based: Gives 40% of credit to both the first- and last-clicked ads and corresponding keyword, with the remaining 20% spread out across the other clicks on the path.

Data-driven Data-driven: Distributes credit for the conversion based on past data for this conversion action. (This is only available to accounts with enough data.)

Source: Google (

If last-click is potentially misleading, then which attribution model should you be using?

Well, to come off as needlessly diplomatic, they all have their virtues and they all have their flaws. So in short, it depends on your goals and sophistication needs. Is your account build simple and straight-forward without multiple funnel points? Then last click is probably fine as it’s efficient, tangible, and it probably doesn’t make much of a difference anyway.

But are you focused on new acquisition and expansion? Then you’re going to want to more closely analyze the performance you’re seeing towards the top of funnel and assign conversion credit accordingly. To this end, your options are first-click, which can be just as obfuscating as last click if you’re not careful, and position-based. (Strangely, Google doesn’t offer its own native option that weighs credit more heavily from the first interaction on in a cascading fashion, which would effectively be the reverse of their time-decay model.)

Time decay would probably be a good one to use if you’re somewhere in between—you want to more heavily assign conversion credit to the last interaction but you’re also interested in discovering the path a user might’ve taken to get there.

Data-driven attribution is a bit more complicated and you can only use it if your account accrues at least 800 conversions and 20,000 clicks within a month (and ideally, you’d want much more than that). This is one I personally haven’t had many use cases for, but you can learn more about it here.

Bottom-line: don’t simply default to last click attribution. There’s a sea of dynamic information to be gleaned about how your audience is converting by utilizing the various conversion attribution models available to you according which is most appropriate for your account and advertising goals. So dive in.

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