On Pigouvian Taxes: A Reply to Scott Sumner

Responding to two blog posts by myself and Kevin Corcoran on skepticism about Pigouvian taxes, Scott Sumner gives an example of a congestion tax in Orange County that has been a huge success.  Scott writes:

This example shows that not all Pigovian taxes are a failure.  Other successes include congestion charges in cities like Singapore, London and Stockholm. 

 

Scott could have added Fairfax County, Virginia, to his list.  I-66 runs from Washington DC through Fairfax County and out toward West Virginia.  66 was a restricted highway: during rush hour, only people in carpools could use it (and there were huge fines for violators).  Yet, 66 was always backed up.  In 2017, the Department of Transportation removed the HOV restriction and opted to switch to dynamic tolling during rush hour.  The tolls would go up or down depending on the volume with the goal of keeping the average speed on I-66 at 55 (the speed limit).  This has been a huge success.  The implementation of dynamic tolling virtually eliminated traffic jams.  This dynamic tolling is a form of tolling is a Pigouvian tax.

It is a Pigouvian tax and one I celebrate wholeheartedly.  In grad school, I traveled 66 a lot. I wasted God knows how many hours sitting in traffic.  When the dynamic tolling was implemented, I could easily decide if the value of my time was worth the toll.  

In our posts, Kevin and I talk about skepticism.  I am skeptical of market failure corrections, but I am not categorically opposed to them.  There are instances where they can work.  As usual, the devil is in the details.

One of the reasons I am skeptical of Pigouvian taxes is that governments can be slow to adjust the tax (either up or down).  There are numerous political factors that get in the way, special interests start to get involved, and just the political process in general is slow.  Thus, a tax may be too high or too low for too long, resulting in suboptimal outcomes.  One of the great things about congestion taxes, especially like the I-66 toll, is that they can be easily adjusted.  The I-66 toll is entirely automated.  It goes up and down fairly quickly to adjust the level of traffic.  No need for votes, lobbying, or other costly procedures.  The adjustment costs are low.

Furthermore, the negative (or positive) effects of the congestion tax are quite quickly realized.  One can instantly see traffic rise or fall with the level of the tax.  The analytical costs of the tax are low.  Conversely, a carbon tax has effects that are very slow to manifest.  Negative (or positive) effects of carbon emissions can take years to emerge.  The analytical costs of a carbon tax are quite high.

Finally, at least in the I-66 case, the tax is collected via a transponder that many vehicles have (or a bill is mailed according to the registration linked to the license plate of the car if no transponder is present).  The tax is instantly collected; there is no need for measurements or audits.  The administrative costs of the tax are low.

I do support congestion taxes.  Having spent many hours sitting in Boston traffic (as I am sure Scott did, too), I wish my home state would do something similar on those highways.  A congestion tax is able to overcome my skepticism.

The point of my posts on market failure corrections is not that such actions should never, ever be done.  It’s not that they are doomed to failure.  Rather, it’s to remind economists and readers of our most basic lessons: there ain’t no such thing as a free lunch.  Market interventions are not costless.  Yet most economists treat them as if they are.  Your standard econ textbook will give just a glib overview of market failure along the lines of: “Markets work great.  But once transaction costs get high, markets fail and government can/should intervene.”  I am trying to inject the natural skepticism of the economist into these decidedly non-economic lines of thinking.  We have to compare real-world alternatives.  Most market interventionists fail to do so: they just see a market failure and assume government intervention will make it better.  We, as economists and scientists, must be skeptical of all plans.  We must look at them realistically.  We must examine the details, for that is where the devil lies.  That skepticism can be overcome.  But it needs to exist.

Interestingly, this is where public choice analysis comes into play.  Without public choice, the advantages of dynamic or automatic tolling isn’t obvious.  But public choice teaches us to examine politics without romance, that the incentives faced by politicians are not the same as incentives faced by people interacting directly in the market with prices guiding them.  To the standard economist, if all else is held equal, having a tax set by a committee or a tax set by automatic dynamic tolling would be equally preferable.  A public choice economist realizes those two methods are not equally preferable.  One would lead to a much worse outcome than the other.

 


Jon Murphy is an assistant professor of economics at Nicholls State University.

READER COMMENTS

Scott Sumner
Sep 13 2024 at 2:01pm

Well said.  One other factor worth considering is whether the proposed Pigovian tax is better or worse than other taxes it might replace.

Craig
Sep 13 2024 at 3:19pm

Paying government for the problems they cause. DC metro is like a 1/4 of the size of NYC but has 10x the traffic. I believe outside of the Washington Monument no building can be taller than the Capitol and there’s only 671k in DC itself. A more natural development would see 2-3mn there and a consequence is that those people are now clogging up I66 with you and instead of questioning the restrictive zoning we’re congratulating the government for whacking these people over the head for $30/day? Nashville, TN has about the same number of people as DC the city, but metro Nashville about 40% the size of DC metro. The problem isn’t the traffic, the traffic is a byproduct of having cut the city’s head off artificially.

Jon Murphy
Sep 13 2024 at 3:24pm

Well, yes and no.

Yes, the District itself has height restrictions.  But the surrounding area does not.  The area got built up to get around those restrictions.

Besides, as the cases with Boston, Orange County, Stockholm, etc., all show, those problems would exist even without height restrictions.  Major cities will necessarily have substantial traffic.  A congestion tax is one way to deal with that problem.

Thomas L Hutcheson
Sep 17 2024 at 11:46pm

Jon, how do you go about deciding when an externality merits a Pigouvian tax or not.   I was rather surprised at the easy advocacy of congestion pricing (whihc would actually be a bit difficult technically) but not net CO2 emissions??

Dylan
Sep 14 2024 at 11:36am

Your standard econ textbook will give just a glib overview of market failure along the lines of: “Markets work great. But once transaction costs get high, markets fail and government can/should intervene.” I am trying to inject the natural skepticism of the economist into these decidedly non-economic lines of thinking. We have to compare real-world alternatives. Most market interventionists fail to do so: they just see a market failure and assume government intervention will make it better.

I’ve probably mentioned this before, but I think this is our biggest point of difference. I don’t see (or at least didn’t see back when I was studying this) the assumption that government is the only or best way to remedy an externality. In my environmental econ classes, where we talked a lot about externalities, we also talked a lot about private action and organizations. For example, I remember community run fisheries as an example of helping to avoid the tragedy of the commons without government regulation.

Even where government intervention was seen as necessary, economists spent most of their time trying to think through what is the minimal amount of intervention necessary to achieve the goal in the most efficient way possible. Cap and trade systems seem to be a good success story, where the government picks the amount of pollution that is acceptable, and lets industry figure out the optimal way to get there. Obviously, there are problems with how politics will interfere in picking the target, but it still lets prices float freely and the market to work.

My complaint (which I outlined in a comment on Scott’s post as well) is that we’ve moved from an era where it felt like the middle 80% of economists were largely in agreement that market based approaches, albeit with some government interference, even if it was just to help assign property rights, were the best ways to deal with externalities. While, rhetorically at least, it now feels like half want nothing to be done and the other half want heavy command and control policies. Hardly anyone seems to still advocate for what I think is likely the best pragmatic approach to deal with large externalities like climate change.

Thomas L Hutcheson
Sep 14 2024 at 5:08pm

So far as I know, no one has ever suggested that taxation of net CO2 emissions is costless, just that it is the _lowest cost (deadweight loss)_  way of net zero by any given date.

Jon Murphy
Sep 15 2024 at 11:39am

So far as I know, no one has ever suggested that taxation of net CO2 emissions is costless

Implicitly, they do.  You’ll find most estimates of carbon emission taxes outright ignore the adiministration costs.  Indeed, it took until 1982 before administrative costs were even incorperated into theoritical modeling.

Don Boudreaux
Sep 15 2024 at 1:06pm

From a July 2024 piece by Hannah Ritchie at Our World in Data:

[I]t’s a robust and consistent result within the scientific literature: today, more people die from cold than heat.

And the numbers aren’t even close: far more people today die from cold than from heat.

So I’ll repeat a question that I often ask: Given this reality, why are so many people today so confident that CO2 emissions are a negative externality? It seems to me that the presumption – rebuttable, to be sure – ought instead to be that CO2 emissions are a positive externality. At the very least, the confidence that so many people today have that humanity should aim to slow global warming by reducing CO2 emissions surely is excessive.

I am seriously interested in a serious answer to this question.

Daniel Kling
Sep 15 2024 at 4:08pm

The non-heat potential problems that I tend to remember are:

Ocean acidification from CO2 messing w/ marine life (where all the dying coral is presumably the canary)
Melting glaciers up north doing something bad to disrupt currents in the Atlantic causing Europe to potentially get a lot colder (and potentially something similar in all the other oceans/places about which I know even less? no clue!)
Various issues with biodiversity since most flora and fauna don’t adapt as rapidly as we do (your mileage will vary on how much you care about that per se – I was born in 1985, so I got hit hard with the “we’re losing 8 cures for cancer from Amazon deforestation” stuff growing up. I discount that now, of course, but it lives on as a gut thing.)
More potential for droughts, floods, and other extreme weather events (this makes some intuitive sense for hurricanes w/ warmer water where they form/strengthen, but I’m not sure if I necessarily expect warming to lead to more extreme outcomes so much as a different distribution of weather events)

As the parentheticals imply, I’m not super confident about the causal mechanisms or likely effects of these, and I’m happy to skeptical of the greens. But I don’t think we can write off their concern about global warming/climate change based on the point that cold is more deadly than heat. They’re not that simpleminded.

E.g., I’m not vouching for the organization that put this together (NRDC), but here’s a list of various expected problems caused by climate change that go beyond things just getting warmer. They’re presumably more interested in this than I am.

If you don’t like those guys, though, I’d check out one of these: https://www.google.com/search?q=problems+with+climate+change+besides+the+heat

 

Warren Platts
Sep 17 2024 at 2:05pm

Why are so many people today so confident that CO2 emissions are a negative externality? It seems to me that the presumption ought instead to be that CO2 emissions are a positive externality.

For once I find myself in agreement with Dr. Boudreaux. We need to be very careful what we wish for. The usual state of affairs during the current geological epoch are 100,000 yearlong ice ages punctuated by brief interglacial periods lasting on the order of 1o to 11 thousand years. The last ice age lasted 11,000 years ago. A 2012 study found:

“Taking the MIS19c analogy [a previous interglacial period very similar to the current one] to its logical conclusion implies that the current interglacial would be nearing its end, provided that CO2 concentrations were ~240 ppm.”

240 ppm seems to be the magic number required to cause glacial inception and the start of another ice age. Needless to say, the inception of another ice age would be far worse than the most paranoid global warming projections. Since we’re at 400 ppm, thanks to humans, we’re currently in no danger. But I can envision a day when people will be clamoring for CO2 subsidies once the current hysteria backfires.

Robert EV
Sep 17 2024 at 2:23pm

These numbers are all averages. If you look at the best interpolated climate charts we were already near a relative maximum for recent interglacials, and now we’re going up even more.

Whether cold or warm whether causes more deaths is variable (note that this is for the US only): https://www.wunderground.com/cat6/Which-Kills-More-People-Extreme-Heat-or-Extreme-Cold

They stressed that one must correct for the seasonal cycle in deaths before using this technique, to remove the influence of the winter influenza season and other non-weather-related factors. Interestingly, they found that major heat waves cause big spikes in the death rate, whereas major cold waves do not: “Severe heat waves often produce large “spikes” in mortality, especially during the 1995 heat wave across the Midwest. However, abnormally cold conditions have little effect on the standardized daily mortality. For example, February 1996, a cold period across much of the United States, produced no spikes in winter mortality levels.”

And from: https://phys.org/news/2020-08-cold-weather-accounts-temperature-related-deaths.html

“With the decrease in the number of cold weather days over the last several decades, we still see more deaths due to cold weather as opposed to hot weather,”  <…> “This is in part due to the body’s poorer ability to thermoregulate once hypothermia sets in, as well as since there are fewer cold weather days overall, people don’t have time to acclimate to cold when those rarer cold days do occur.”

Which could indicate that fewer cold days may actually decrease the ability of people to adapt to the cold, which could result in more (or at least equal) mortality.

I’m just devil’s advocating here. What the situation is will vary over the world and will require good studies to parse out multivariate effects. Changing the global mean temperature – putting more energy into the system – is going to result in deaths due to other circumstances that aren’t counted among hypothermia or hyperthermia related deaths. I wish you well in calculating those statistics.

Robert EV
Sep 17 2024 at 2:24pm

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Don Boudreaux
Sep 15 2024 at 7:07am

Pardon me if this point has been made here or in earlier posts, but using a toll on a highway as an example of a successful tax is odd. It’s a price. If the road were privately owned and operated, access to it would be priced such as to keep traffic at optimal levels. As it happens, I-66 – and, I presume, also the Orange County highway mentioned by Scott – are owned and operated by government. The government, here acting akin to a private company, charges prices for access during high-volume times. But because it’s government, the price charged is called a “tax.”

Because highways could easily be supplied exclusively by the market – and because, if highways were so supplied, the prices charged would match demand with supply just as readily as do the prices charged all other private-sector firms – using tolls on  highways owned and operated by the government as evidence of the potential success of Pigovian taxes doesn’t quite work.

 

Scott Sumner
Sep 15 2024 at 7:42pm

“If the road were privately owned and operated, access to it would be priced such as to keep traffic at optimal levels.”

Is that true?  Might not the price be set at a level that maximizes profits?

Knut P. Heen
Sep 16 2024 at 7:22am

That is the problem with taxes too. If they can charge people only if there is congestion, expect a lot of congestion on public roads.

Jon Murphy
Sep 16 2024 at 8:03am

Except, as we see with congestion taxes, that’s not necessarily true.

Knut P. Heen
Sep 16 2024 at 11:55am

I was imprecise. Don’t expect more road capacity. Taxes reducing demand will reduce congestion, but it kills the incentive to increase road capacity. They lose both the tax revenue and have to pay for the investment.

Anyway, Don is right, the argument for public roads is that it is a public good, but that is no longer true when there is congestion. A private actor would at least have some incentive to increase the road capacity if there is congestion.

Scott Sumner
Sep 16 2024 at 2:50pm

To be clear, I am in favor of private roads in many situations.  But when roads are publicly owned, I see congestion tariffs as being Pigovian taxes.

Jon Murphy
Sep 17 2024 at 8:58am

the argument for public roads is that it is a public good

Are they?  I don’t think so.  They are private goods (or club goods, depending).  They are certainly excludable and are rival in consumption.

Jon Murphy
Sep 17 2024 at 9:04am

Don’t expect more road capacity.  Taxes reducing demand will reduce congestion, but it kills the incentive to increase road capacity.

But one doesn’t necessarily need more road capacity, at least in the near term.  But in a dynamic model, there could be more road capacity if the demand subseqently grows (say, NOVA keeps seeing population increases.  Or the Metro keeps breaking down).

Robert EV
Sep 17 2024 at 2:16am

Which roads/communities pay the price in increased traffic for the benefit of the toll payers on I-66? And what is this price?

Jonathan Monroe
Sep 17 2024 at 4:36am

Part of the attraction of congestion taxes is that the answer is quite close to “nobody”. A highway with traffic moving at 55mph gets more people where they are going than one with stop-start traffic. In effect, the marginal rush hour driver on a congested road waits until the traffic clears before getting to their destination, and gets in other people’s way while waiting, so getting them to wait at home until the dynamic toll drops is win-win.

On a net basis, shunpikers replace ratrunners and the number of people driving on residential streets to avoid the congested highway remains constant – if the number of people actually reaching their destination on the highway doesn’t drop, the number avoiding it doesn’t increase.

How does this work in practice? With congestion, the people who really care about getting into the city for 8am pay in lost sleep, leave early to beat the traffic, sit in a traffic jam with other people leaving early to beat the traffic, and get into the city around 8am anyway (with a high level of uncertainty due to traffic delays). The people who don’t care as much don’t leave early to beat the traffic, get stuch in traffic, and arrive well after 8am. With a toll, the people who really care pay the toll, get to sleep longer, and arrive predictably at 8am. The people who don’t care as much travel at a time when the dynamic toll is lower.

The only way this doesn’t work is if the experience of using a free-flowing tolled highway is so much better than sitting in traffic that it generates sufficient “induced” (really unsuppressed) demand to drive the toll so high that it creates a new generation of shunpikers (something similar happened in London, when a lot of commercial traffic for which the Kengestion charge is just a cost of doing business shifted to daytime deliveries once the low-value private cars were priced our). But unsupressing demand is usually a social win, and in any case if you have enough supressed demand for suburb-to-city travel that “induced” demand is a problem you should be building commuter rail because it scales an order of magnitude better than roads.

Robert EV
Sep 17 2024 at 2:07pm

Thanks. I wonder as real-time traffic apps become more common whether the same results can be had without a toll.

Re: Getting to the office. This is why I typically head to work in the early afternoon and try to head home after traffic has died down. This, and congestion due to concentration of high-rise buildings in particular sections of a city, really highlight the toll (no pun intended) we pay for government zoning laws and private sector business preferences.

you should be building commuter rail because it scales an order of magnitude better than roads

It has its own issues in time losses and sleep deprivation to avoid congestion (whether parking to take the rail, or on the rail itself). I still prefer the politically unacceptable decentralization of jobs.

Jon Murphy
Sep 17 2024 at 9:01am

The I-66 toll has actually reduced congestion on alternative routes (namely US-50) as well.  Before, 66 was a HOV (3+ if I recall correctly, though it could have been 2+) only road for certain hours.  That pushed all non-HOV traffic to US-50.  When they went to the toll, the traffic was able to reallocate to 66.

Robert EV
Sep 17 2024 at 2:07pm

Good to know that people aren’t crowding residential streets and making them more dangerous.

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