OK. So we know that Bookscan doesn't cover sales at Walmart. But chances are you don't buy much poetry at Walmart. Do a search for poetry at walmart.com and it will say NOT SOLD IN STORES. Poetry isn't Stieg Larssen. We get it.
Why should we be skeptical of Bookscan numbers? It's what the Book Industry uses to judge how everyone else's books are doing. The first rule of Book Publishing is to LIE about how many books you're actually selling. You lie about how many books you've printed, you lie when you say you're going to reprint books. Publishers lie. So Bookscan numbers are an independent way to generally see how books are selling.
But what are Bookscan numbers really a metric of, in terms of poetry? Poetry sales are tiny, outside of a handful of core books that always sell. Harriet mentions Rumi. The Prophet is probably one. Poets published by every publisher aren't counted in. If you buy Leaves of Grass, well, which Leaves of Grass did you buy? They are separated in sales by ISBN. So there's a flawed dynamic. Chances are sales of Walt Whitman last week would give sales of W. S. Merwin a shot for their money if all editions were taken into effect.
And bestseller lists only count for new books. So the beat-up used Walt Whitman you bought off a blanket by the park doesn't count. But why does that matter? If we're going to write trend pieces based on actual influence, extrapolating from bestseller lists, well, it matters. When Frank O'Hara's poems showed up on "Mad Men" they quickly sold out of most stores. Which had one copy (if that) on hand of Meditations in an Emergency. What was the possibility for sales after Don Draper flipped through the book? And then read a poem a the end of the episode? Enormous. From poets and non-poets alike. What was the reality in bookstores? Even with great distribution by Grove Press, there wasn't many copies in your neighborhood store. (They strangely STILL haven't released a version that looks exactly like the one Don read in that episode and put an AS SEEN ON MAD MEN sticker. That would have gotten table quantities ordered.)