As you probably know, measuring aggregate web activity based on Page Views in Google Analytics is not a good idea.

For instance, imagine a site with 2 content topics: Economics and Politics. There are 5 pages about Economics and 10 about Politics.

You look at your analytics. Economics gets 500 views per month. But wow! Politics gets 1000.

Its obvious, therefore, that Politics is much more popular and should get most attention in terms of UX, optimisation, etc.

Wrong

Look deeper and you discover that each topic gets exactly the same number of visits: 100 each.

It is simply because Economics has twice as many pages that it appears twice as popular using Page Views.

(Why it has twice as many pages is a separate question. Perhaps there is much more information on that topic? Or maybe it has the same volume of information but uses a different content design approach? Or perhaps the information has been poorly planned and arbitrarily separated among too many pages?)

This shows that measuring or comparing activity using Page Views (including Unique Page Views) at an aggregate level is a bad idea. Visits are far better.

The problem is that the Google Analytics' default Behaviour report does not count total Visits at a topic level, not even in Content Drilldown. (Content Drilldown does show total Unique Views, but that is not the same as total Visits.)

This is where Content Groups step in

Content Groups flatten issues caused by varying numbers of pages and show what users are really interested in.

Read the full article "Content Groups and Google Analytics".