Picture this, you’re looking over the metrics for your most recent Google Ads Campaign, but you notice that as you go back over previous days, the metrics are changing from what they originally were. For example, on Sunday, your number of conversions was 30, but after checking back on Friday, it looks as though there were 35 purchases on Sunday. So, what is actually going on?
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How Google Measures Conversions
Put simply; Google records conversions with the help of cookies and the last-click attribution model. So, conversions that happen in a few weeks can still count as having happened today.
How Does This Work?
It starts with the last-click attribution model. But to understand the last-click attribution model, we first need to understand what a cookie is. Whenever a user clicks on a Google Ad, if they have allowed cookies on their browser, a memory of that action will be stored. The default lifetime of a cookie is 30 days; however, this can be changed by the ad owner to either 60 days or 90 days in their Google Ads account.
Another essential feature of a cookie is that, with the last-click model, a cookie’s “age” is reset to zero each time a user clicks on an ad. This cookie will then last for 30 days in the default setting.
Last-Click Attribution Model
Now that we know what a cookie is and how it works, we can better understand Google’s last-click attribution model. The way the model works has a relatively large clue in its name. When a conversion is recorded from a particular user, the conversion date is recorded as the date of the last ad the user clicked.
Let’s take a look at an example for some more clarity. Three possible conversion outcomes can happen once an ad has been clicked.
A user makes a purchase on the same day they click the ad for the first time.
This is the simplest and most ideal scenario. For example, suppose a user clicks your ad on January 1st; if they make a purchase on the same day, the conversion will be recorded as having happened on January 1st.
A user clicks an ad and makes a purchase within 30 days.
Say that a user clicks an ad on January 1st; if they then make a purchase within 30 days, the conversion will still be recorded as having happened on January 1st. So, for example, if their first and only click occurs on January 1st, but they make a purchase on January 15th, the conversion will be recorded as having happened on January 1st.
Note that this only counts if they have yet to click on another ad in-between their first time clicking the ad and making a purchase.
Within 30 days of a user’s first click, they click on another ad before purchasing.
Once again, a user clicks an ad on January 1st, but then again on January 7th, the user clicks another ad. If they then make a purchase on January 13th, the conversion will be recorded as having happened on January 7th. This occurs because each time an ad is clicked, the age of the cookie is reset to zero, and according to Google’s last-click attribution model, the most recent click gets credited for the purchase.
What Happens If I Don’t Want To Wait 30 Days To See My Conversions?
If you’re looking for another way to track your conversions, which doesn’t rely on waiting 30 days to see the final result, Google has another way of reporting conversion metrics.
In October 2019, Google released a new column labeled Conversions (by conv. time). All purchases made on any given day are recorded as conversions, regardless of the first click. This means that the only thing that mattered was the day the conversion occurred. So, for example, if a user clicked an ad on January 1st and made a purchase on January 8th, the conversion would be recorded as having occurred on January 8th.
Which Method Of Conversion Is Better?
Both ways of recording conversions have their benefits; ideally, they should be consulted when running your advertising campaigns.
For example, if you’re looking to calculate your cost per action (CPA) or return on ad spend (ROAS), it could be better to use the original Google conversions column, since you will have a more accurate idea of the value of each click brings. But, if you’re looking for a better measure of your cash flow, it may be more beneficial to use the Conversion (by conv. time) column for your calculations.
Bringing It All Together
In summary, Google measures conversions using a last-click attribution model, which means that the conversion date is recorded as the date of the last ad the user clicked. So, for example, if a user clicks an ad and makes a purchase within 30 days (the default lifetime of a cookie), the conversion will be recorded as having happened on the date of the first click. However, if a user clicks on another ad before making a purchase within 30 days, the conversion will be recorded as having happened on the date of the most recent click.
Google also has a separate column called Conversions (by conv. time) that records all purchases made on a given day as conversions on the same day, regardless of when the first click occurred. Both of these ways of measuring conversions can be useful for understanding the effectiveness of your advertising campaigns.