Gmail Meter is an Apps Script which runs on the first day of every month and sends you an email containing different statistics about your Inbox. 

In a similar way to how Google Account Activity gives key stats about how you've used your Google Account, Gmail Meter gives you different types of statistics that will help you analyse your Gmail habits. 
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  • Volume Statistics show you the number of important and starred messages, the number of people who sent you emails, and more. Volume statistics can be very useful in determining how you are using email efficiency tools like Priority Inbox.
  • Daily Traffic gives you an estimate of when you receive messages and when you send them during a given month. For example, in the graph below you can see how the peaks in my “Sent” curve indicates that I write emails in spurts.
  • Traffic Pattern lets you get a sense of your overall email activity over the past week.
  • Email Categories tells you how you are managing your Inbox. 
  • Time Before First Response shows you how long it takes you to reply, and how long it takes others to reply to you. 
  • Word Count tells you whether you are writing long emails.
  • Thread Lengths help you understand whether you participate in long conversations resulting in long threads.
  • Top Senders and Top Recipients help you identify who you communicate with more frequently.
It is easy to set up Gmail Meter. First, go to Google Docs and open a Spreadsheet.

Click on Tools > Script Gallery. Search for “Gmail Meter” and click Install. You will now see a new menu item called Gmail Meter on your spreadsheet.

Click on Gmail Meter > Get a Report. You can then choose the type of report. Preparing a report may take some time and you will get an email once the report is ready.

If you would like to know more about how this script works, be sure to check this tutorial.