Return Path has just published the new version of its famous "Inbox Placement Benchmark Report". I'll leave it to you to download the new version of this report, and I'll focus on just one section of the report, the one dedicated to Gmail tabs.
Placement and open rates in Gmail's "Promotion" tab (versus "Primary" tab)
This is probably the first time that we receive such a nice summary table of the impact of the "Promotion" tab in Gmail. We can notice that for some sectors the impact is almost zero (Communication, Clothing, Nonprofit, ...) while for others, it is not negligible ... and not always in the way we imagine.
We can see that for some sectors, the opening rate of messages is much better when they are in the Promotion tab! This means (as Badsender has always said) that what is good for the quality of the email box of your customers is good for you (even if you are respectful of your subscribers :-D ).