I honestly think there is no other reason to ever visit that tab and that’s probably why it took me so long to realize a time-based comparison was even possible.
As you can see “Compare” let’s you pick a “Date range” to compare against. In the example I compare the 7-day period starting on 11/26 with the 7-day period starting on 11/19.
Notice that on the resulting table below you not only see the absolute numbers (blurred in this example), but also the % changes.
Very useful to spot trends and monitor the impact of changes you’ve made!
The ugly caveat: Works for Campaigns only
There is one big, ugly caveat unfortunately. You can only run comparisons on the account and campaign levels. Comparing Ad Groups or even specific keywords only isn’t possible.
Another speed bump: You first have to define filters for the campaigns you want to compare.
The filters you’ve created become immediately available in the “All Campaigns” drop down on the “Home” tab.
The workaround: “Dimensions” and Pivot Tables
There is one option left if you do want to get more granular, but shy away from purchasing third-party PPC tools. You can run a report from the “Dimensions” tab and set the view to “Time”.
When you now export the report as a .csv file you can import it into Microsoft Excel and turn it into a Pivot table. You can then add the % change metrics as needed and also chart the data.
Let me know if you have any questions in the comments below. I’m happy to help.