The last interaction attribution model (also known as the last touch attribution model) assigns 100% credit for a conversion to the last interaction on a conversion path. 

Google Analytics uses this model by default for multi-channel funnel (MCF) reports. There is a common misconception that the last touch attribution model is innately bad or flawed. And that when you do attribution modelling you must abandon the last touch model. But this is not true. 

For example, let us suppose you are an FMCG (fast-moving consumer goods) company like Tesco or Walmart. Since you sell products (like toothpaste) that involve the least amount of buying consideration, your customers’ conversion paths tend to be short. 

So you do not need to assign more conversion credit to the first and middle interactions on your conversion paths. Consequently, you can use the last touch attribution model. So the last touch model has its own use and place. 

The following examples will help you in understanding how the conversion credit is calculated in the case of the last interaction attribution model:

Example-1: Consider the following conversion path with a path length of four:

This conversion path can also be represented by the following data table:

Here your customer was exposed to various campaigns in the following order before the conversion occurred on your website: 

Campaign A > Campaign B > Campaign B > Campaign C.

Under the last interaction model, the last touch gets 100% credit for the conversion. So conversion credit distribution would look like the one below:

• Campaign A gets 0% credit for the conversion.
• Campaign B gets 0% credit for the conversion.
• Campaign C gets 100% credit for the conversion.

Table of Contents

Toggle

Get my best selling books on Attribution Modelling

• Learn to implement attribution modelling in your organisation
• Understand the customer purchase journey across devices
• Determine the most effective marketing channels for investment

 Click book covers to find out more

Example-2: Consider the second conversion path with a path length of three:

This conversion path can also be represented by the following data table:

Under the last interaction model, the last touch gets 100% credit for the conversion. So conversion credit distribution would look like the one below:

• Campaign A gets 100% credit for the conversion.
• Campaign B gets 0% credit for the conversion.
• Campaign C gets 0% credit for the conversion (as campaign C is not on the conversion path).

Total conversion credit for campaign A so far

 = (conversion credit for campaign A on the first conversion path + conversion credit for campaign A on the second conversion path) / 2 

= (0% + 100%) / 2 

= 50%

Total conversion credit for campaign B so far 

= (conversion credit for campaign B on the first conversion path + conversion credit for campaign B on the second conversion path) /2 

= (0% + 0%) / 2

= 0%

Total conversion credit for campaign C so far 

= (conversion credit for campaign C on the first conversion path + conversion credit for campaign C on the second conversion path) /2 

= (100% + 0%) / 2 

= 50%

Example-3: Consider the third conversion path with a path length of two:

This conversion path can also be represented by the following data table:

Now the conversion credit distribution would look like the one below:

• Campaign A gets 0% credit for the conversion.
• Campaign B gets 100% credit for the conversion.
• Campaign C gets 0% credit for the conversion (as campaign C is not on the conversion path).

Total conversion credit for campaign A so far

= (conversion credit for campaign A on the first conversion path + conversion credit for campaign A on the second conversion path + conversion credit for campaign A on the third conversion path) /3  

= (0% + 100% + 0%) / 3 

= 33.33%

The total conversion credit for campaign B so far 

= (conversion credit for campaign B on the first conversion path + conversion credit for campaign B on the second conversion path + conversion credit for campaign B on the third conversion path) /3  

= (0% + 0%+ 100%) / 3 

= 33.33%

Total conversion credit for campaign C so far 

= (conversion credit for campaign C on the first conversion path + conversion credit for campaign C on the second conversion path + conversion credit for campaign C on the third conversion path) / 3 

= (100% + 0% + 0%) / 3

= 33.33%

Now if we assume that there are only three conversion paths in our selected time period, then the sum of conversion credit for campaigns A, B and C under the last interaction attribution model would be 33.33% + 33.33% + 33.33% = 99.99% (rounded off to 100%). 

Since the sum of the conversion credit for three campaigns is 100%, this proves that our conversion credit distribution calculations are all correct. 

Other articles on Google Analytics Attribution Models

1. First Interaction Attribution Model in Google Analytics
2. Linear Attribution Model in Google Analytics
3. Time Decay Attribution Model in Google Analytics
4. Position-Based Attribution Model in Google Analytics – Tutorial
5. Last Non-Direct Click Attribution Model in Google Analytics
6. Last Google Ads Click Attribution Model in Google Analytics
7. Data-Driven Attribution Model in Google Analytics – Tutorial
8. Learn to set up Data-driven attribution model in Google Analytics
9. Default & Custom Google Analytics Attribution Models Explained
10. Which Attribution Model to use in Google Analytics?
11. How to Create Custom Attribution Model in Google Analytics