#10 - One year ago, a municipality banned dishwasher

[Adam Tyson]

What officials tried or did not try doesn't matter here, ssnasir, nor does the question of whether the ban worked, because all we are trying to determine is why the phosphates coming out of the plant decreased. Was it, as the author said, because some people switched, or could it be due to some other cause? If officials tried to stop people from bringing in those detergents from out of state, what would that tell us about why the water treatment plant is emitting less phosphates? Did they succeed, or did they fail? If they failed, could it still be that people switched anyway?

Focus on the conclusion: "it is clear that some residents did switch to phosphate-free detergents." What's the evidence? "phosphate pollution from the municipal wastewater treatment plant decreased." What do we need to know to determine whether that is a good argument or not? Whether that decrease is related to people switching or not.