I've been experiencing a gradual but significant traffic decline since around the time of the Penguin 4.0 release.
As I've read through the other Penguin threads there seem to be several members reporting this same phenomenon too. Enough so that I'm hoping this thread can just address that issue.
I get that as sites get released from Penguin that other sites' rankings will be affected, and possibly what I notice is just that. But I'm curious what other webmasters are noticing and what they suspect.
For me, the drop seems to be near 15%.
You could easily explain that just by a number of important keywords dropping from #2 to #3, so I'd be happy enough with that explanation.
But I don't necessarily get the impression that most of my "main" keywords have really experienced a hit. It seems more like it must be the long-tail that has been affected.
Also, I started to experience fluctuations off and on 2 weeks before the official Penguin 4.0 announcement, which doesn't really fit the expected.
Also, this isn't a site that has ever had any Penguin related issues (nor manual actions). I wasn't expecting much of an effect from this algorithm change.
Some other members in some other threads mentioned that possibly other substantial algo changes had occurred during this same time period. I'm wondering what people think at this point.