The Performance reports tab at www.google.com/adsense is designed to provide more insight into not just how much you're earning, but what impacts those earnings.
If your blog is responsive and you've placed responsive adsense ad codes on it, you can track the performance of your responsive ad units by viewing the Ad units report on the Performance reports tab.
To access the "Ad Units" report,
==> Sign in to www.google.com/adsense
==> Click on "Performance reports" tab
==> On the left sidebar, click "Ad Units"
Right there, you will see the earnings, number of clicks, number of page views etc of each responsive ad unit on your blog. Each responsive ad unit will be identified by the name you used when you created them.
The performance of all responsive ad units on your blog is shown under the “Responsive” label in the "Ad sizes" report. This is where you will see the total number of clicks, ad request CTR, CPC and estimated earnings of all the responsive ad units on the blog.
Clicking on the "Responsive" label will break down the performance further, day by day.
If you want to track the sizes of the ads that have been served from your responsive ad units, you can view the Creative sizes report.