"Despite cleaning up several times a week, they found roughly the same amount of trash each time they returned." This is evidence they are succeeding at limiting the amount of trash. If you pick up trash and there is no trash the next time you go, you probably didn't really need to do the pickup.
“If you pick up trash and there is no trash the next time you go, you probably didn't really need to do the pickup.” That’s not what it says. Every time they went back, there was litter again. New litter. Picking up the litter does not succeed in stopping people from littering in that spot.
Yes, I understand. And if they hadn't picked up any litter there would be (something like) twice as much litter. You don't really need a "litter cleanup crew" in places where litter is a one-time thing.
*Any* litter in a spot is bad. It doesnt matter if it’s 10 lbs of litter or 20 lbs of litter, it’s pretty much equally unappealing. And the overall point is: *contrary to popular belief*, cleaning up a spot to make it free of litter for a moment does not result in a people ceasing to litter there.
I'm seriously doubt that this is a "popular belief." I've always understood litter abatement to be an ongoing task. I would think you'd have to have largely never been outside in a city to believe otherwise.
For people who honestly believe that finding litter in a location is a one-time thing, I don't think they have enough common sense to understand your point.