On the Limits of Expert Credibility: Theory and an Application to Climate Change?

On the Limits of Expert Credibility:Theory and an Application to Climate Change (h/t FE) is an interesting paper. I'm not sure I believe it, but it is interesting (particularly so after reading Krugman on why people don't understand [[Comparative advantage]]; h/t Timmy).

The "Conclusions" section is a bit odd. Having spent the paper trying to demonstrate that interested parties will try to buy off the messenger, i.e. the media, they then try to explain the media's non-accuracy by Morris's (2001) model of political correctness instead of their own results. I don't understand that.

The abstract is better, and explains their model and conclusions:

A neutral expert sends an informative message to an uninformed voter. An interested party can pay a cost to replace the expert's message with its own. The more informed is the expert, the greater is the interested party's incentive to replace the expert's message. In equilibrium, making the expert more informed has no effect on the voter's beliefs and strictly reduces social welfare. The model thus implies an endogenous limit on how credible a purported expert can be. I apply the model to public skepticism about climate change.

This is of course a model; but it helps explore something I've thought about a bit, which is "how to get the general public to understand GW". The problem, of course, is that whilst *I* know who are experts and whom to trust and distrust, Joe Public doesn't really know, and cannot evaluate the science for himself. So they try to model this: the expert can send a message, but interested parties can pay to replace that message (which simplifies the real world, where the voter gets both messages, but hey this is but a model).

One of the assumptions of the model is only stated in the conclusions, and then only implicitly:

I show that because voters cannot separate true experts from credentialed advocates, public opinion cannot, in general, converge to expert opinion in the presence of motivated, interested parties.

The assumption that voters can't separate is necessary, but may not be true. In fact I think it is quite likely false: people make a semi-conscious decision to believe dubious sources because it suits them (again, shades of Krugman). Further, the model has become so idealised that I can't tell how large the costs to the interested parties are, and what they might be compared to in the real world. Also, as they show (section 3.2, case ii) if the costs are "too high" then the interested parties don't bother pay and the voter gets the expert opinion.

making the expert more informed has no effect on the voter's beliefs and strictly reduces social welfare is I think dubious. What they mean is, that under certain of their assumptions, voter opinion isn't affected by increasing expert credibility. But the "interested parties" need to spend more buying off the message. They interpret this as a loss of social welfare. But actually it represents a transfer of wealth from a "Bad" party (one trying to buy off the true message must be Bad, I think we can agree) to a neutral one (those apparently-credentialled experts. We might call them Bad too, because they are lying-for-hire, but assuming they don't believe it and are only doing what they are paid for (otherwise, they wouldn't need to be paid, no?) they are less-Bad than those who are paying for the lying. So contrary to the papers stated result, I think that increasing expert credibility increases social welfare (again, shades of Krugman; do read him, please).

More like this

A more accurate theory about global warming/cooling/climate change is quite simple. Some sorry good for nothing nutjob dumbass at the top of the new world order foodchain is demanding MONEY in order to fund various socialist/communist projects and using this scam called global warming as a front to obtain the funds. All involved should be charged with fraud, striped naked, given 25 lashes with a whip, then be sent to prison in Sibria naked with only one candle to warm the place. This whole thing is one big massive maarxist fraud and everyone involves deserves maximum punishment.

> they are less-Bad than those who are paying for the lying

Or more in need of the money, which in terms of utility transfer amounts to the same thing, more or less. I'm thinking of some of the emerituses living off meager civil servant's pensions, damn right they milk Exxon-Mobile for what they are worth... so, the denial industry as a pension augmentation scheme?

By Martin Vermeer (not verified) on 05 Jan 2012 #permalink

AGW & EGU need to publicize awards more. Quotations from awardees need to mention in passing the awards.

By David B. Benson (not verified) on 05 Jan 2012 #permalink

When I read the paper, I'll be looking for signs of a false premise leading to a gobbledygook conclusion. Wish you'd look a bit askance at Krugman, who has become a hyper-partisan. Unlike you, he's just a talk the talker.

[I think you'll find what K has to say about CA, and R, interesting -W]

By Paul Kelly (not verified) on 06 Jan 2012 #permalink

This seems apropos.

[Interesting, but fundamentally wrong. The distinction he makes - public debate rarely settles, scientific debate does - is not because scientific evidence is better - though it is - but because of the method of scrutiny; the ability to detect good from bad. Whereas in public debate (GW most obviously) evidence shown to be bad is continually re-presented -W]

By Rattus Norvegicus (not verified) on 06 Jan 2012 #permalink

Oh yeah,

that Paul Krugman who is the only one who understands the debt (his words: "government debt does no matter"), and who loves Ponzi schemes, such as global economy? :-)

But I agree, it is difficult to find a sane economist...


Alexander, can you please provide a direct link to the Krugman quote? I've read his "Nobody understands debt", and it surely is not part of *that* column. In fact, in the last paragraph it says "So yes, debt matters", which makes me rather skeptic (not septic) that you can provide any link to Krugman claiming "government debt does no(t) matter".

Hello Macro,

thanks for comment! To be more specific, a had in my mind this Krugman's words:

"First, families have to pay back their debt. Governments donât â all they need to do is ensure that debt grows more slowly than their tax base. "

- and if he writes, governments do NOT NEED to pay back the debt, I think it is fair to say that "gov debt does NOT matter".

Well, Krugman might write in the end that debt DOES matter, but then he is inconsistent, at least. All I agree with him (in general), that root of the crisis is NOT gov debt (but private debt and financial deregulation is...)


[Hmm, to me quote marks normally mean a direct quote. Reinforced by "his words" I'd expect ''his words: "government debt does no matter"'' to mean he had actually said that. ''all they need to do is ensure that debt grows more slowly than their tax base'' is a very very different thing to "debt does not matter". Even I can explain why it is very different, and I'm not even an Evil Economist. Do you really not understand the difference?

I can give you a personal example if it helps: when I was young I took out a mortgage, an interest-only life-assurance type one: it was all the rage at the time. My part of the mortgage was £27k ish. Alas, like many others of the type, it didn't grow as it was supposed to and only paid out £17k. They kept on sending me worried-sounding letters about how my policy wouldn't pay off my mortgage. But I didn't care: £10k, which was a fortune to me when I took out the mortgage originally, what fairly unimportant 25 years later.

That isn't an exact analogy, of course. But the central point remains: govts need to pay the interest on their debt. If govt income goes up, then they can either pay off their debt, or (fortified by the new income) go deeper into debt. Err, just like normal people who may choose to trade up to a larger mortgage if their income goes up.


Sorry, Alex, but I still disagree with your translation of what Krugman says. As Krugman notes, the importance is in the tax base - debt ratio. Only in that sense does the debt (not) matter.

William and Marco,

thanks for comments, again. Points taken, I was not exact and analogy understood.

BTW, I do not think economists are evil (just like climatologists are not), but just clueless (of, that endless growth no matter what), but that is different topic...




once again, to your quote of Krugman:

''all they need to do is ensure that debt grows more slowly than their tax base'' - when somebody *assumes* GROWING tax base, it is still a Ponzi economist, I think. And, if the tax base is not growing, but stagnating or contracting, debt is a hell of a problem (as we can see now...)


[I don't understand you. Assuming a growing tax base appears entirely natural, and is supported by past experience. Those who have problems with debt (Greece, Italy) don't have that problem because their tax base is shrinking, but because the rates they have to pay are growing -W]


I know this is not an economic blog, but is it rational to expect growing tax base in a contracting economy?

[Greece is a special case, as are the last couple of years. But even on that pic, the tax base has grown by 9 axis units over 10 years. So we're talking about the long term. About climate, not weather -W]


Greece might be a special case, but UK is not much better either.

Given peak oil (peak energy) issue, I do not agree with your weather/climate analogy (i.e. that we will be back othe n track of growth). Economy will cool down for many, many years, I think.


[Ah, but that is not the mainstream position. The view you started of criticising was based on the assumption of an increasing tax base, which is what "everyone" expects, just as everyone expects increasing GHG emissions. If you disagree with those assumptions, well, fair enough. But you need to make that clear up front. Otherwise you're like some GW skeptic who starts off by just saying "I don't believe in GW" and after some time clarifies that yes, he believes in the science and he believes the physics and he accepts the temperature record: he just thinks that future emissions will be too small to cause a problem. Again, its a view, but its not the mainstream one -W]