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Last Updated: May 26, 2022

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

If you are a new player in your niche then you may need more brand awareness than your established competitors. Consequently, your advertising goals would likely be more brand-building centric. 

For that reason, you may need to assign more conversion credit to the interactions which initiated the conversion process. In that case, you should use the first touch attribution model. 

However, there is one technological limitation associated with the first touch model which you need to be aware of. 

In Google Analytics, the attribution window (aka lookback window) cannot be longer than 90 days. Therefore, if the first user interaction occurred more than 90 days ago then Google Analytics will not be able to record that interaction as the first interaction. 

So if your sales cycle is more than 90 days long then there is always a strong possibility that the first touches reported by GA are not the true first user interactions with your brand or campaigns. 

You need to be aware of this limitation if you decide to use the first touch attribution model and your sales cycle is more than 90 days long. 

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The following examples will help you to understand how the conversion credit is calculated in the case of the first interaction attribution model:

Consider the following conversion path with a path length of four:

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

Under the first interaction model, the first touch gets 100% credit for the conversion. Here Campaign A is the first touch on the conversion path. So the 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.

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 first interaction model, the first touch gets 100% credit for the conversion. Here Campaign B is the first touch on the conversion path. So 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).

The 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 

= (100% + 0%) / 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% + 100%) / 2 

= 50%

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 

= (0% + 0%) / 2 

= 0%

Consider the third conversion path with a path length of two:

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

Now under the first interaction model, the 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).

The 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 

= (100% + 0% + 100%) / 3 

= 66.67%

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% + 100% + 0%) / 3 

= 33.33%

The 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 

= (0% + 0% + 0%) / 3 

= 0%

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 first interaction attribution model would be:  66.67% + 33.33% + 0% = 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. Last Interaction Attribution Model in Google Analytics Explained
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