Attribution – What PPC Data Really Shows for eCommerce

What is Attribution:

I live in the world of eCommerce and attribution is very important to understand. Let’s start the discussion by defining exactly what I mean by attribution.

Attribution can be a lot of things:

“Attribution is the process of identifying a set of user actions (‘events’) that contribute in some manner to a desired outcome, and then assigning a value to each of these events” – IAB Attribution Primer

Attribution is therefore very broad, for the sake of this discussion, let’s scope the definition down to Attribution in AdWords Search for eCommerce. In this post I will use empirical data to explain how attribution affects AdWords Search for eCommerce businesses.

What did I do?

I had long discussions with several PPC experts (most of them Googlers) and we all came to one main conclusion involving attribution within AdWords Search for eCommerce:

What is the impact of assisted click conversions on an AdWords search account?

If we listen to the experts out there, then you might have a keyword like “smartphone” and this keyword almost never converts (a defender). However, a keyword like “samsung s3 smartphone” will have all the last-click conversions (a striker).

If you only have one last-click conversion on “smartphone,” but that keyword leads to 10 assisted conversions, then obviously that is an important keyword. There is a lot of hidden data not evident if you only look at the last-click conversions.

If your keyword sits in the top 3 position, then you already have that keyword in a good position. If the keyword sits below 3, then that keyword is potentially “under-valued” and could be bid up.

However, let’s look at the data first.

What did I analyze?

I examined 3 months of data for three large eCommerce clients, accounting for conversion lags by starting from 30 days ago. I have compared both accounts managed by Finch and accounts managed by others.

Based on my discussions with Googlers and other AdWords experts, we came to the conclusion that in order for it to be attribution within AdWords Search for eCommerce the data must show twice as many assisted conversions as last-click conversions.

Problem statement:

Are there any keywords that have twice as many assisted conversions as last click conversions within AdWords Search?

If so, what is the impact of these keywords?

For the analysis, I only looked at keywords sitting in position 3.0 or lower and had received at least 1 click. If they had 1 or more assisted conversions, but zero last-click conversions, then they also fit this description.

For the analysis part, I compared the keywords I found with the total number for any keyword with either:

a) a last click conversion and/or
b) an assisted conversion

So basically anything adding value to the account (not including impression-assisted conversion value)

What I Found

International Home Goods Retailer:
139 out of 12,018 keywords fit this description = 1.16%
The 139 keywords of the 1,461 keywords with conversions = 9,5% represents:

  • 3.81 % of the total clicks
  • 9.82 % of the impressions
  • 3.49 % of the cost
  • 0.32 % of total conversion value
  • 5.57 % of total click assisted conversion value

UK Home and Garden Retailer:
18 out of 17,112 keywords fit this description = 0.11%
The 18 keywords of total 2,596 keywords with conversions  = 0.7% represents:

  • 5.49 % of the total clicks
  • 8.21 % of the impressions
  • 4.81 % of the cost
  • 0.93 % of total conversion value
  • 9.57 % of total click assisted conversion value

Danish Electronics Retailer:
61 out of 10,487 total keywords fit this description = 0.58%
The 61 keywords of the 1,590 keywords with a conversion = 3.8% represents:

  • 1.65 % of the total clicks
  • 2.40 % of the impressions
  • 1.38 % of the cost
  • 0.05 % of total conversion value
  • 6.53 % of total click assisted conversion value

Thoughts on data:

The data shows that there are very few keywords matching my definition of attribution. The main reason: most keywords function as both assisted-click conversions and last-click converters. I found very few keywords functioning either as a strictly assisted-click converting keyword or a last-click converting keyword.


If you define attribution with AdWords Search for eCommerce as keywords that are so broad that they will almost never convert, but will have a lot of assisted conversions, then attribution within AdWords Search is almost non-existent. Very few keywords have this characteristic!

The assumption that keywords play a role as either first-click converters or last-click converters is not supported by the data. The story of “defenders” and “strikers” is fun, and intuitively believable, but in practice there are very few keywords that could be strictly labeled as “strikers.” The data shows 90%+ of keywords are actually “allrounders.” Keywords sometimes work as assisted conversions and sometimes work as last-click conversions. When you focus attention on keywords in the last-click converting role, you will actually be looking at 95% of the revenue-generating traffic.

Look for yourself in your AdWords account. Filter for “Search Funnel -> Click assisted conv / Last click conv.” Set that higher than 2 and add in another filter looking for keywords below position 3.0. You will most likely find only a couple of keywords.

The way we define and evaluate attribution is far too generic and should be updated. The only way to identify the best ways to optimize your AdWords efforts is with more data and less opinions.


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