Msz, it's based on how people Rate you. Higher Rating means higher title. Check mine for example, I'm a Sage but theres people whos posted more than me that still arent Sage.
the rating is not based on the number of post but how those post where rated. if you did nothing but post spam you might not ever get a scholar but if you only post relivant and usefull information then you will get a much higher score in no time.