When I read a poem in the New Yorker, I get frustrated by the lack of verbal economy. I think of Larry Hart:
Have you met Miss Jones, someone said as we shook hands
She was just Miss Jones to me
Then I said Miss Jones, you're a girl who understands
I'm a man who must be free
Then all at once I lost my breath
Then all at once was scared to death
Then all at once I owned the earth and sky
Now I've met Miss Jones, and we'll keep on meeting til we die
Miss Jones and I
That's like 90 words or so, and ten are "Miss Jones." Take the first 90 words of a New Yorker poem and nothing has happened yet. Even in a shorter one.
Prose should be concentrated in the same way. Every page must have worthwhile ideas. Even the presentation of background material must do so with a sense of urgency. In other words, it's not "here's what you should know before you understand my argument," but: this is how my argument shapes our understanding of what you might already know by way of background.