It looks like the impressions follow an exponential (geometric? someone will surely correct me) distribution which is what you would expect if it was based on w

It looks like the impressions follow an exponential (geometric? someone will surely correct me) distribution which is what you would expect if it was based on what people click on. If it was something different where niche outlets were featured more often than their "share", that would imply manipulation and would be a cause for concern.