joined:Apr 1, 2016
I don't have an idea on if the two things can be correlated,
It will be very difficult to show any meaningful correlation between the two since most sites are in the "not-reviewed" status. Conversely, I would speculate that sites that have the "reviewed" status probably are doing well in terms of RPM, but that would be that Google is most likely prioritizing for review the largest and most successful sites, so it would be difficult to draw any conclusion from that.
I went back and checked my rpm for all time on a monthly basis. I see a distinct pattern, every January there is a dip in RPM ("the January effect") and then there is a recovery in February. This recovery is never a full recovery, every year the RPM steps down. I have been fortunate in that my traffic has been growing steadily since I started, so I suspect that there is negative correlation between traffic and RPM. Which seems paradoxical to me. I further suspect that falling traffic would further erode RPM, which would be even more paradoxical.
My theory is that when one starts a new sites Google has little information with which to rank the site, so it limits queries that the site can rank for to queries that a very specifically in-line with the topic or interest of the site. One gets few users but those users are likely interested in the site so more likely to engage with the ads. As the site gains trust with Google it begins to rank for more queries but those may be for search terms that are less well targeted to your site. As result one sees more users but fewer ad clicks, thus a drop in RPM. If at some point the site begins to fall out of favor with Google, the site then continues to ranks for as many queries but ranks lower and the users coming to sites are even less likely to engage with content and ads so one sees a further drop in RPM, which ends up being the beginning of a death spiral.
A death spiral, because many publishers react to dropping in earnings by adding more ads or different ads to the point of impact the overall site experience. The causes further drop in user engagement and a likely a further drop in rankings.
One always needs to be reminded that the quality of ones site is a relative measure, relative to competitor sites. What ranked on page 1 last year may no longer rank this year, not because of any changes to your own site but due to changes to the competitive environment that surrounds it.