I've never been concerned with the absolute numbers of people who read poems. It's obvious, that with a third of a billion native English speakers and many more who speak English as a second language, Milton has a audience orders of magnitude bigger now than when he lived. What matters is that readers, serious readers who buy enough of the likes of Steven Hawking, Douglas Hofstadter, Richard Wright, Philip Roth, A. S. Byatt, Stephen Jay Gould, Chinua Achebe, Salmon Rushdie, Umberto Eco, and Steven Pinker to make them bestsellers, do not buy or read contemporary poetry in English. That is an unprecedented situation.
Whatever the ultimate cause of that may be, the proximate cause is easy find. When an educated man or woman walks into a bookstore thinking it would be nice to know something more about evolution, there are many serious books from which to choose, books whose authors have taken great pains in writing and organizing so that a general reader can follow the evidence and arguments. The same is true in physics, philosophy, and even mathematics. That they aren't the books specialists in their fields write for each other is irrelevant: poetry has never been written for specialists.
Closer to home, when that same educated man or woman wants to read a novel or a short story, one can be sure that the authors of nearly every book in the store will have tried to write an opening that excites the reader's interest and will have worked hard to make sure that the remainder of the story keeps that interest through clear writing and strong characters or plot or both.
In bitter contrast, that same reader pulling a book of contemporary poetry from the shelves is not unlikely to be confronted with something like this beginning:
Look at this picture then describe it
as areas of the body at which
whatever is sensed is vibration
during singing, tell me
do you feel it do you
feel it here or here and now
what does it feel like does it
feel real good to you?
(first two stanzas of Garret Kalleberg's "From a Psychological Atlas")
or this one:
Murderous little world once our objects had gazes. Our lives
Were fragile, the wind
Could dash them away. Here lies the refugee breather
Who drank a bowl of elsewhere.
(all of Anne Carson's "EPITAPH: ZION")
Not every time. But whatever the merits of those particular poems or poets, do you think that educated, interested reader will be encouraged to look further on the poetry shelves? Or will it be just another reminder that poetry is unfathomable and dull?