Is duplicate content responsible for the strong fluctuations in the indexed pages of my website?

If you notice continuous fluctuations in the number of the indexed pages over a longer period of time, then the reason for, or a sign thereof, could very well be Duplicate Content.

Visibility Index trend for Around the turn of 2012, a prominent zig-zag pattern emerges in which the visibility drops sharply every few weeks and then regains the loss.
Strong fluctuations and a noticeable up and down in the number of indexed pages could indicate a duplicate content problem.

In order to evaluate the cause of these fluctuations and recognise or even exclude a possible duplicate content problem, an Onpage analysis of the affected site is necessary.

To get to the bottom of such fluctuations and find initial analysis options, please see: