My recent post, Air Pollution Reduces Health and Wealth drew some pushback in the comments, some justified, some not, on whether the results of these studies are not subject to p-hacking, forking gardens and the replication crisis. Sure, of course, some of them are. Andrew Gelman, for example, has some justified doubt about the air filters and classroom study. Nevertheless, I don’t think that skepticism about the general thrust of the results is justified. Why not?
First, go back to my post Why Most Published Research Findings are False and note the list of credibility checks. For example, my rule is trust literatures not papers and the new pollution literature is showing consistent and significant negative effects of pollution on health and wealth. Some might respond that the entire literature is biased for reasons of political correctness or some such and sure, maybe. But then what evidence would be convincing? Is skepticism then justified or merely mood affiliation? And when it comes to action should we regard someone’s prior convictions (how were those formed?) as more accurate then a large, well-published scientific literature?
It’s not just that the literature is large, however, it’s that the literature is consistent in a way that many studies in say social psychology were not. In social psychology, for example, there were many tests of entirely different hypotheses–power posing, priming, stereotype threat–and most of these failed to replicate. But in the pollution literature we have many tests of the same hypotheses. We have, for example, studies showing that pollution reduces the quality of chess moves in high-stakes matches, that it reduces worker productivity in Chinese call-centers, and that it reduces test scores in American and in British schools. Note that these studies are from different researchers studying different times and places using different methods but they are all testing the same hypothesis, namely that pollution reduces cognitive ability. Thus, each of these studies is a kind of replication–like showing price controls led to shortages in many different times and places.
Another feature in favor of the air pollution literature is that the hypothesis that pollution can have negative effects on health and cognition wasn’t invented yesterday along with the test (we came up with a new theory and tested it and guess what, it works!). The Romans, for example, noted the negative effect of air pollution on health. There’s a reason why people with lung disease move to the countryside and always have.
I also noted in Why Most Published Research Findings are False that multiple sources and types of evidence are desirable. The pollution literature satisfies this desideratum. Aside from multiple empirical studies, the pollution hypothesis is also consistent with plausible mechanisms and it is consistent with the empirical and experimental literature on pollution and plants and pollution and animals. See also OpenPhilanthropy’s careful summary.
Moreover, there is a clear dose-response effect–so much so that when it comes to “extreme” pollution few people doubt the hypothesis. Does anyone doubt, for example, that an infant born in Delhi, India–one of the most polluted cities in the world–is more likely to die young than if the same infant grew up (all else equal) in Wellington, New Zealand–one of the least polluted cities in the world? People accept that “extreme” pollution creates debilitating effects but they take extreme to mean ‘more than what I am used to’. That’s not scientific. In the future, people will think that the levels of pollution we experience today are extreme, just as we wonder how people could put up with London Fog.
What is new about the new pollution literature is more credible methods and bigger data and what the literature shows is that the effects of pollution are larger than we thought at lower levels than we thought. But we should expect to find smaller effects with better methods and bigger data. (Note that this isn’t guaranteed, there could be positive effects of pollution at lower levels, but it isn’t surprising that what we are seeing so far is negative effects at levels previously considered acceptable.)
Thus, while I have no doubt that some of the papers in the new pollution literature are in error, I also think that the large number of high quality papers from different times and places which are broadly consistent with one another and also consistent with what we know about human physiology and particulate matter and also consistent with the literature on the effects of pollution on animals and plants and also consistent with a dose-response relationship suggest that we take this literature and its conclusion that air pollution has significant negative effects on health and wealth very seriously.
Hugh Rockoff does a 72 pp. deep dive on Milton Friedman on bailouts. This is an excellent paper, as he also considers Friedman’s columns and spoken words over the years and he also fleshes out Friedman’s thoughts on what we now call “shadow banks” (he worried about them). Friedman was willing to accept a fair number of bailouts, here is one excerpt:
In the bailout of Continental Illinois, a case that Friedman thought had been handled well, depositors and other creditors were protected, but shareholders were mostly wiped out and management was replaced. The protection of depositors and other creditors created an advantage for large banks: they could raise funds more easily because they, like Continental Illinois, were “too big to fail.” However, Friedman thought that as long as shareholders and managers were forced to pay dearly when a financial institution was bailed out there would still be an adequate incentive for bank managers to exercise prudence.
For Friedman this meant that in the case of financial institutions the benefits of a bailout might outweigh the costs.
And more speculatively:
No one can channel an economist as brilliant and creative as Milton Friedman. Nevertheless, having come this far I will make an attempt. I believe that it would have been consistent with his earlier views for Friedman to have been “reluctant to condemn” the program of bailouts undertaken in 2008, to use the phrase that he used when questioned about the rescue of Long–Term Capital Management. I think he would have recognized that the repos issued by Lehman Brothers and other investment banks were similar to uninsured deposits in commercial banks, thus making possible a destructive panic. In other words, he would have recognized the logic of the contention that 2008 was a “run on repos” and similar to earlier financial panics (Gorton, Laarits, and Metrick 2018). He might have reminded us of the consequences of the failure to provide help for the BoUS in 1930. However, he might well have been critical of the structure of the bailouts, especially with respect to how various classes of stakeholders were treated.
I recall being excoriated in 2009 for suggesting that Friedman would have endorsed some version of the bailouts of that time.
In the 1920s immigration to the United States was restricted with quotas which were designed to reduce the number of immigrants from Italy and Eastern Europe, then considered to be low-quality immigrants. One unintended consequence was that the number of immigrant scientists from these areas also declined. The awesome Petra Moser and Schmuel San have an excellent new paper documenting the cost on US innovation and patenting.
Naturalization data indicate a dramatic decline in the arrival of new ESE-born scientists after the quotas. Until 1924, arrivals of new ESE-born immigrant scientists were comparable to arrivals from Northern and Western Europe (WNE), who were subject to comparable pull and push factors of migration.1 After the quotas, arrivals of ESE-born scientists decline significantly while arrivals from Northern and Western Europe continue to increase. Combining data on naturalizations with information on scientists’ university education and career histories, we estimate that 1,165 ESE-born scientists were lost to US science under the quota system. At an annual level, this implies a loss of 38 scientists per year, equivalent to eliminating the entire physics department of a major university each year between 1925 and 1955. For the physical sciences alone, an estimated 553 ESE-born scientists were lost to US science.
To estimate the effects of changes in immigration on US inventions, we compare changes in patenting per year after 1924 in the pre-quota fields of ESE-born US scientists with changes in patenting in other research fields in which US scientists were active inventors before the quotas. This identification strategy allows us to control for changes in invention by US scientists across fields, for example, as a result of changes in research funding. Year fixed effects further control for changes in patenting over time that are shared across fields. Field fixed effects control for variation in the intensity of patenting across fields, e.g., between basic and applied research.
Baseline estimates reveal a large and persistent decline in invention by US scientists in the pre-quota fields of ESE-born scientists. After the quotas, US scientists produced 68 percent fewer additional patents in the pre-quota fields of ESE-born scientists compared with the prequota fields of other US scientists. Time-varying effects show a large decline in invention by US scientists in the 1930s, which persisted into the 1960s. Importantly, these estimates show no preexisting differences in patenting for ESE and other fields before the quotas.
Canada which did not implement quotas did not see a similar decline. One interesting case study which is quite astounding in its way:
A case study of co-authorships for the prolific Hungarian-born mathematician Paul Erdős illustrates how restrictions on immigration reduced collaborations between ESE-born scientists and US scientists. Erdős moved to the United States as a post-doctoral fellow at Princeton, and became a professor at Notre Dame, travelling and collaborating with many US scientists. As a Hungarian citizen, however, Erdős was denied a re-entry visa by the US immigration services in1954, and not granted re-entry until 1963. To examine how these denials affected Erdős’ collaborations with US scientists, we collect the location of Erdős top 100 coauthors at the time of their first collaboration. These data show that Erdős’ collaborations shifted away from the United States when he was denied re-entry. Between 1954 and 1963, 24 percent of Erdős’ new co-authors were US scientists, compared with 60 percent until 1954. These patterns are confirmed in a broader analysis of patents by co-authors and co-authors of co-authors of ESEborn scientists, which indicates a 26 percent decline in invention by scientists who were directly or indirectly influenced by ESE-born scholars.
As you might suspect from the Erdos example, scientists in the US became less not more productive without the benefits of cooperation with Eastern European scientists.
Some of the scientists denied entry to the US in the 1920s went to Israel instead and innovated there so their genius was not entirely lost to the world.
Photo: Paul Erdos with Terrence Tao. Attribution, either Billy or Grace Tao, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons
That is the topic of my latest Bloomberg column, here is one excerpt of some super-simple (but neglected) arguments:
Education is another area where Friedman’s ideas seem newly relevant. Friedman was a strong supporter of school choice, but over time the movement stalled, as a variety of studies showed scholastic gains from school-voucher programs that were either modest, zero or negative. Advocates for school choice then moved on to the argument that vouchers allow parents to choose the kind of education they want for their children, whether or not test scores go up. That argument, too, went nowhere.
Then came the pandemic, when millions of American parents encountered a public school system that didn’t seem to care too much about educating their children. Schools stayed closed or offered inferior remote instruction, and generally followed their own bureaucratic imperatives. All of a sudden, home schooling, charter schools, private schools, micro-schools — in short, an entire host of “school choice” alternatives — rose in popularity. It remains to be seen how much those trends will stick, but Friedman may yet win this intellectual battle, at least partially.
And it’s not just the bureaucracy, it’s what’s taught in the classroom. Consider critical race theory and other instructional practices affiliated with wokeism. Whatever your views on this movement, it seems clear that it provokes strong and perhaps irresolvable differences among parents, teachers and administrators. Within a single public school district, those matters will probably never be settled to everyone’s satisfaction. Rather than pursuing a polarizing “fight to the death,” perhaps all sides can see that the case for school choice is stronger and more compelling than they had thought.
There are periodic attempts to knock Milton Friedman off his pedestal. For the most part, however, his legacy remains strong.
And who was the guy who predicted the recent problems with the FDA?
I’ve long been suspicious of the “deep deep” roots theory of southern Italian stagnation, given the Neapolitan Enlightenment in the 18th century. This explanation, however, at least in principle makes more sense to me:
The provincial gap in human capital at the time of Italy’s unification is a plausible explanation for the North–South divide of the following decades. We show that the roots of the literacy gap that existed in 1861 can be traced back to Napoleonic educational reforms enacted between 1801 and 1814. We use exogenous variation in provincial distance to Paris to quantify effects, linking the duration of Napoleonic control to human capital. If the south had experienced the same Napoleonic impact as the north, southern literacy rates would have been up to 70 percent higher than they were in 1861.
That is from M. Postigliola and M. Rota in European Review of Economic History. Might Napoleon be underrated?
In many places commemorative plaques are erected on buildings to serve as historical markers of notable men and women who lived in them – London has a Blue Plaque scheme for this purpose. We investigated the influence of commemorative Blue Plaques on the selling prices of London real estate. We identified properties which sold both before and after a Blue Plaque was installed indexing prices relative to the median prevailing sales prices of properties sold in the same neighborhood. Relative prices increased by 27% (US$165,000 as of July 2020) after a Blue Plaque was installed but not in a control set of properties without Blue Plaques, sold both before and after a Blue Plaque was installed in close proximity. We discuss these findings in relation to the theory of magical contagion and claims from previous research suggesting that people are less likely to acknowledge magical effects when decisions involve money.
Abstract: How important are legal systems to economic performance? To address this question, I focus on a historical period from colonial Shanghai, where quite different legal systems operated in the International Settlement andFrench Concession. In particular, employing novel historical data, I examine 1903–1934 land value discontinuities at the border between these Settlements. Substantial discontinuities were found in the 1900s, with higher land values associated with the International Settlement. However, by the 1930s, this land value advantage of the International Settlement had disappeared. A closer look at the institutions reveals that the French Concession adapted its operation to be more business friendly, under competition from the neighboring International Settlement. This suggests that the French legal system per se was not a barrier to economic growth, but rather it could function well if interpreted and implemented properly. This paper thus adds to evidence that formal legal system is not a key determinant of economic performance.
That is from Mingxi Li, who is on the job market this year from UC Davis.
I was honored to visit his home and painting studio, here is the audio, video, and transcript. Here is part of the CWT summary:
David joined Tyler to discuss the fifteen (or so) functions of good art, why it’s easier to write about money than art, what’s gone wrong with art criticism today, how to cultivate good taste, the reasons museum curators tend to be risk-averse, the effect of modern artistic training on contemporary art, the evolution of Cézanne, how the centrality of photography is changing fine art, what makes some artists’ retrospectives more compelling than others, the physical challenges of painting on a large scale, how artists view museums differently, how a painting goes wrong, where his paintings end up, what great collectors have in common, how artists collect art differently, why Frank O’Hara was so important to Alex Katz and himself, what he loves about the films of Preston Sturges, why The Sopranos is a model of artistic expression, how we should change intellectual property law for artists, the disappointing puritanism of the avant-garde, and more.
COWEN: Yes, but just to be very concrete, let’s say someone asks you, “I want to take one actionable step tomorrow to learn more about art.” And they are a smart, highly educated person, but have not spent much time in the art world. What should they actually do other than look at art, on the reading level?
SALLE: On the reading level? Oh God, Tyler, that’s hard. I’ll have to think about it. I’ll have to come back with an answer in a few minutes. I’m not sure there’s anything concretely to do on the reading level. There probably is — just not coming to mind.
There’s Henry Geldzahler, who wrote a book very late in his life, at the end of his life. I can’t remember the title, but he addresses the problem of something which is almost a taboo — how do you acquire taste? — which is, in a sense, what we’re talking about. It’s something one can’t even speak about in polite society among art historians or art critics.
Taste is considered to be something not worth discussing. It’s simply, we’re all above that. Taste is, in a sense, something that has to do with Hallmark greeting cards — but it’s not true. Taste is what we have to work with. It’s a way of describing human experience.
Henry, who was the first curator of modern and contemporary art at the Metropolitan Museum in New York, was a wonderful guy and a wonderful raconteur. Henry basically answers your question: find ways, start collecting. “Okay, but I don’t have any money. How can I collect art?” You don’t have to collect great paintings. Just go to the flea market and buy a vase for 5 bucks. Bring it back to your room, live with it, and look at it.
Pretty soon, you’ll start to make distinctions about it. Eventually, if you’re really paying attention to your own reactions, you’ll use it up. You’ll give that to somebody else, and you’ll go back to the flea market, and you buy another, slightly better vase, and you bring that home and live with that. And so the process goes. That’s very real. It’s very concrete.
COWEN: As you know, the 17th century in European painting is a quite special time. You have Velásquez, you have Rubens, you have Bruegel, much, much more. And there are so many talented painters today. Why can they not paint in that style anymore? Or can they? What stops them?
SALLE: Artists are trained in such a vastly different way than in the 17th, 18th, or even the 19th century. We didn’t have the training. We’re not trained in an apprentice guild situation where the apprenticeship starts very early in life, and people who exhibit talent in drawing or painting are moved on to the next level.
Today painters are trained in professional art schools. People reach school at the normal age — 18, 20, 22, something in grad school, and then they’re in a big hurry. If it’s something you can’t master or show proficiency in quickly, let’s just drop it and move on.
There are other reasons as well, cultural reasons. For many years or decades, painting in, let’s say, the style of Velásquez or even the style of Manet — what would have been the reason for it? What would have been the motivation for it, even assuming that one could do it? Modernism, from whenever we date it, from 1900 to 1990, was such a persuasive argument. It was such an inclusive and exciting and dynamic argument that what possibly could have been the reason to want to take a step back 200 years in history and paint like an earlier painter?
It is a bit slow at the very beginning, otherwise excellent throughout.
An excellent book, the author is Robert Kanigel and the subtitle is The Making of a Scientific Dynasty. It is strongest on the role of mentors and lineages in scientific excellence, the radically inegalitarian and “unfair” nature of scientific achievement and also credit, and it offers an interesting look at the early days of the NIH. Here is one excerpt:
But Brodie simply saw no reason to become an expert in an area to launch a study of it. Rather, as Sid Udenfriend says, “he would just wander into a new field and make advances that people fifteen years in the field couldn’t.” Poring through scientific journals didn’t appeal to him; picking the brains of colleagues did. “He’d go up to you,” Jack Orloff remembers, “and say, ‘Tell me what you know about X and Y.’ Sometimes he’d already know a lot, but he could come across as almost stupid.” Indeed, he could seem downright ignorant, asking disarmingly simple, even hopelessly naive questions, like a child. But as one admirer notes, “He’d end up asking just the questions you should have asked ten years ago.”
Beginning around 1955, the big stir at LCP was over serotonin. (“When the experiments were good, we called it serotonin,” Brodie would later recall…”When I heard it pronounced serotonin, I knew the experiments were bad and I stayed home.”)
Martin Zatz, a veteran of Julius Axelrod’s lab and a scientist with an uncommonly broad cast of mind, was talking about mentoring and its role in science. “Are you going to talk about the disadvantage of the mentor chain?” he asked me, smiling broadly.
What’s that? “That you don’t get anywhere,” he replied, now quite serious, “unless you’re in one.”
Recommended. Why are there not more excellent conceptual books on the history of science?
That is a new NBER working paper by Wolfgang Keller and Caroline H. Shiue, here is the abstract:
This paper studies the economic consequences of the West’s foray into China after the Opium War (1839-42), when Western colonial influence was introduced in dozens of so-called treaty ports. We document a turnaround during the 19th century in the nature of China’s capital markets. Whereas before the Opium War, coastal cities were of relatively minor importance, the treaty port system of the West transformed China into an economy focused on coastal areas and on international trade that aligned with the trading interests of the West. We show, first, that the West had a positive impact on China’s economy during the 19th century. It brought down local interest rates, and regions under Western influence exhibited both higher rates of industry growth and technology adoption. Second, the geographic scope of influence went far beyond the ports, impacting most of China. Interest rates fell by more than a quarter in the immediate vicinity of the ports and still by almost ten percent at distances of 450 kilometers from treaty ports. The development of China was not simply propelled by its own pre-1800 history, or by post-1978 reforms. The nearly 100 years of semi-colonization have shaped China’s economy today as one focused on the coastal areas.
As both Alex and I have said before, economics is still a discipline where you can put forward non-PC results without being destroyed for it.
An elegant essay by Saumitra Jha on why tolerance between Hindus and Muslims evolved in India’s port cities.
[W]here do institutions of tolerance emerge? Combining the historical accounts, the fieldwork, and the data, it became clear that such institutions develop in very specific places, where two conditions were satisfied. First, Hindus and Muslims needed to have incentives to work together: for example, engaging in business relationships that complemented each other, rather than competed against one another. Second, this complementarity had to be robust: it had to be difficult for one group to replicate or simply steal the source of the others’ complementarity.
One important set of examples of these were ports—like Mahatma Gandhi’s own hometown, Porbandar—that had traded to the distant Middle East during the medieval period. For one month a year, for close to a thousand years, Mecca had been one of the largest markets in the world during the Hajj—and one had to be Muslim to go to Mecca. This gave Muslims in ports—in India, but also on the African coasts, the Malay peninsula, and beyond—a strong advantage in overseas trade and shipping. And, yet, this advantage nonetheless benefited the communities they connected by sail.
Further this complementarity in overseas trade came from a trading network that was intangible, and so impossible to seize, and the scale of the Hajj was so large it was impossible for a Hindu to replicate. Not surprisingly, then—before being disrupted by European colonial interventions beginning in the 16th century—Muslims had dominated overseas trade across the Indian Ocean, from the coasts of Zanzibar to India, Malaysia and beyond, as far as China.
Ports emerged at natural harbors along India’s medieval coasts to accommodate these trading relationships. These ports also witnessed not just the emergence of rules but also beliefs and organizations that supported trade, inter-group trust, and religious tolerance. So much so, that even three centuries later—after Muslim trade advantages had ended due to European colonial interventions, and many of the ports themselves had silted up and become inaccessible to trade—this legacy of beliefs, norms, and organizations continued to shape the way people interacted with one another. The institutions of peace and tolerance outlived the economic incentives that had once sustained them.
Photo Credit: MaxPixel.
The most developed thesis of that book was that capitalist economies were in a state of constant excess supply (overproduction) whereas centrally planned economies were in a state of constant excess demand (shortage), and he drew out with minute detail all the implications of this analysis. I remember raising arguments from his book in my general equilibrium class in university, surely annoying the professor. Olivier Blanchard once told me he had a similar experience. Kornai’s book was extremely popular among young rebellious economists who wanted to change the world.
In 1980, his magnum opus, Economics of Shortage, came out. Whereas his earlier work on the economics of planning was mostly theoretical (all that literature was very remote from how planning was done in reality), this was the first book to propose a systematic and powerful analysis of how the socialist economy really worked in practice. Starting with the concept of the soft budget constraint (state-owned enterprises in socialist economies that were making losses would never shut down), he explained how this led to increasing demand by enterprises, making them barely responsive to price variations. These increased demands led to generalised shortages that deeply influenced the behaviour of enterprise managers, consumers and planners.
That is from a broader appreciation by Gérard Roland. Here is one original Kornai piece on the topic. Here is a later ungated piece. Here is Eric Maskin on different theories of the soft budget constraint.
Yes, I am talking about the new seven-volume set Architectural Guide to Sub-Saharan Africa. I am now about halfway through volume II, and will read the rest, albeit slowly. The books have plenty of text and also a lot of quality photographs. While they are easy to read, they are not actually fast going.
These books have dozens of authors, so a systematic review misses the point. But just think: do you need to read yet another largely political history of Africa, detailing the conflict in Biafra, the fall of apartheid in South Africa, and the Mugabe dictatorship in Zimbabwe? At what I hope are your current margins, what exactly are you going to learn?
Should you instead read seven volumes about how Africans (and sometimes non-Africans) have built Africa? Its homes. Its businesses. Its government buildings and non-profit centers. Its churches and mosques. What Africa looks like and why. Every significant discussion is accompanied by a relevant photograph.
Is that not a more important learning?
Where else can you find a sub-chapter “Beyond Design: Finnish Architects in Senegal”? Which are in fact the most notable vistas in the Nouakchott fish market? Why does it seem that no building in Mauretania is next to any other building in Mauretania? (I am reading the West Africa volume, obviously.)
Definitely recommended, a notable achievement.
Here is the audio, video, and transcript. Here is part of the CWT summary:
He joined Tyler to discuss whether we’ve gotten better or worse at analyzing risk, the dangerous urge among policymakers to oversimplify the past, why being a good military commander is about more than winning battlefield victories, why we’re underestimating the risk that China will invade Taiwan, how to maintain a long view of history, what set Henry Kissinger apart, the usefulness of war games, how well we understand China and Russia, why there haven’t been any major attacks on US soil since 9/11, the danger of a “soldier class” in America, his take on wokeness and the military, what’s needed to have women as truly senior commanders in the armed forces, why officers with bad experiences should still be considered for promotion, how to address extremists in the military, why he supports a draft, the most interesting class he took at West Point, how to care for disabled veterans, his advice to enlisted soldiers on writing a will, the most emotionally difficult part and greatest joys of his military career, the prospect of drone assassinations, what he eats for his only meal of the day, why he’s done writing books, and more.
COWEN: If we had to shrink one capacity of the military, say, by 50 percent, and double the capacity of another, what would you pick to shrink and what to expand?
MCCHRYSTAL: This is always the tough one. I tend to think that the maneuver warfare part that we have created for ground warfare in Europe or in the Mideast is probably somewhere where we have to accept some risk. We have to have fewer capabilities there. You could even argue maybe the number of aircraft carriers — big capital things.
I think where we can’t afford — and therefore, I would invest — is in really good people. Now, that seems like a simplistic answer, but we are going to need very crafty people at things like cyber warfare. We’re going to need very innovative people. We’re going to need people with cultural acuity, which means language skills, and that’s going to be more important. So if I was advocating, I’d be leaning toward resourcing harder in those areas.
COWEN: Now, of course, your father was a general. You come from a military family. Why is it that military recruitment, right now, is so well predicted by having had a parent in the armed forces? What’s driving that? And how can we take advantage of that to recruit additional people?
MCCHRYSTAL: Well, we’ve taken advantage of it to the point where it may be counterproductive now. When I would travel the battlefields and go to small bases, invariably, the sergeant or lieutenant in charge was the son or daughter of a friend of mine. In one way, it’s comforting because you know people have entered the service with open eyes and clear expectations, and they make good soldiers, but you don’t want a soldier class in America.
Definitely recommended, there is also a segment about disabled veterans and their rights. And again here is Stan’s new book Risk: A User’s Guide, co-authored with Anna Butrico.
I am going to pick Jack Butler Yeats (1871-1957, Sligo) as Ireland’s greatest artist. And yes he was the brother of William Butler Yeats and son of the artist John Butler Yeats, notable in his own right.
Wikipedia offers the following useful description of Jack Yeats:
His favourite subjects included the Irish landscape, horses, circus and travelling players. His early paintings and drawings are distinguished by an energetic simplicity of line and colour, his later paintings by an extremely vigorous and experimental treatment of often thickly applied paint. He frequently abandoned the brush altogether, applying paint in a variety of different ways, and was deeply interested in the expressive power of colour. Despite his position as the most important Irish artist of the 20th century (and the first to sell for over £1m), he took no pupils and allowed no one to watch him work, so he remains a unique figure.
I don’t think there are images I could show to convince you that Yeats should stand above the other contenders. His signature expressionist works are thick with three-dimensional texture, and they look like crap on-line. I am fortunate to have seen a large exhibit of them lately in Dublin. When I first saw some many years ago, I thought they were a splotchy mess, a kind of second-rate Gaelic Kokoscha, but they hold up and improve remarkably well with time. Everything is where it ought to be.
Here is a “more normal” picture by Yeats:
His scenes are more animated, more impudent, more multi-faceted, and fresher than those of any other Irish painter. It is easy to imagine him still inspiring painters today, Irish or otherwise, and I don’t think the same is quite true for the other names surveyed. There is something “whole greater than the sum of the parts” that makes Yeats a clear, easy, and I think (mostly) consensus choice for Ireland’s greatest artist. And he certainly was “Irish enough” to count.
Here is a good Christie’s short essay, mixed in with six high-quality images of works recently up for sale. Oh, and here is one of the expressionist horse paintings after all: