[SilasX]

>The purpose of plastic bag taxes isn't to "price-in" an externality;

Maybe, maybe not; I was responding to a poster who was justifying it on that basis.

>More generally, the language of economics ("pricing-in externalities") doesn't make sense when discussing irreversible damage to the environment:

>When you can't repair the damage, the idea of "pricing-in" externalities is just confused thinking. (You can't buy a new planet...

Well, you can repair the damage from plastic bags.

>2. For any consumer behavior that causes irrevesable damage to the environment, the cost is at once too large to quanify

If your model contains infinities, it's automatically unhelpful; that takes you into Pascal's Wager territory. If the damage is infinitely bad, then it it would justify draconian measures against even trivial risks of too many plastic bags. But however bad they are, they're not infinitely bad. Such a model would justify arbitrarily high bag fees, not some piddling ten cents with the hope of changing long-term consumer behavior.

[zardo]

>If your model contains infinities, it's automatically unhelpful; that takes you into Pascal's Wager territory. If the damage is infinitely bad, then it it would justify draconian measures against even trivial risks of too many plastic bags. But however bad they are, they're not infinitely bad. Such a model would justify arbitrarily high bag fees, not some piddling ten cents with the hope of changing long-term consumer behavior.

Sometimes that's the reality of the situation, there are things that cannot be priced. That's why we don't consider a murder tax an acceptable way to deal with homicide.

[SilasX]

We also don't treat murder as being infinitely bad, and we reject policies that would decrease the murder rate because they would cost us in terms of something else we value e.g. privacy and convenience.

[zardo]

I didn't mean to imply that it has infinitely negative monetary value. I mean that it is a sort of wrong that cannot be undone by money.

[SilasX]

It's the same principle -- however bad some harm X is in the abstract (be it death or environmental catastrophe), it doesn't justify arbitrary measures to fight it, be it more cameras tracking your movement or $20/kg taxes on plastic bags, because in every practical sense the actual harm is bounded.

[nmrm2]

> Well, you can repair the damage from plastic bags.

Maybe. Maybe not. Maybe you can, but the costs to the environment involved in doing so are prohibitive. In any case, I don't think it's totally obvious that this is actually possible ATM.

> If your model contains infinities, it's automatically unhelpful; that takes you into Pascal's Wager territory

Yeah, well, reality > model. Unless we colonize space, destroying earth = infinity. So the implication of your statement is that pricing is a bad model for certain types of environmental damage. However...

> would justify draconian measures against even trivial risks of too many plastic bags.

...the realistic impact of most types of irreversible environmental damage has no known bound, but is not infinite.

Difficult-to-bound unknowns also make it impossible to quantify damages a priori at the level of detail necessary for pricing. Again, reality > model, so accurate pricing is a bad mechanism.

I think there are reasonable arguments against plastic bag bans. But trying base policy on an accurate accounting of the cost of long-term or irreversible environmental damage is a fool's errand in many cases.

(Also, note that my point is that in general, pricing environmental externalities is weird. Plastic bags aren't even nearly the best example of this, but are illustrative of the most common solution -- don't price, disincentivize.)

[SilasX]

It sounds like you're saying you don't know how bad X is relative to other things, and nobody can make an estimate, but it's definitely not infinity, and the possibility of X favors your preferred policy over others.

That doesn't sound like it justifies any one tradeoff over another, nor tell us how we should decide to.

[specialist]

What's your best estimate for cleaning up the Great Pacific Garbage Patch?

You've heard of the precautionary principle?