The professionalization of poetry, or the balkanization, has come out of the fact that when you apply to most creative writing programs, you have to choose your genre.
Robert HassYou only had widespread literacy and books that people could afford in the middle of the 19th century. Did more people read poetry at the turn of the 20th century when there were about fifty million people?
Robert HassMy suspicion is that once you have literacy in place, the readership has not changed very much.
Robert Hass