Please, explain and give results of your campaign that lasts a fair long time with an eye on getting those results.
Perhaps these two posts will bring you some answers:
link 1,
link 2. Besides, read among first posts of the forum and look at those supporting the campaign. Furthermore, at the bottom of OP you can also see some more support for this campaign. I know, it's not pure statistics to say so, but it's almost impossible to quantify results by math...
I hope this helps.