Monday, April 24, 2017

How Bad is Peer Review? Evidence From Undergraduate Referee Reports on the Currency Unions and Trade Lit

In a recent paper, Glick and Rose (2017) suggest that the Euro led to a staggering 50% increase in trade. To me, this sounded a bit dubious, particularly given my own participation in the previous currency unions and trade literature (which I wrote up here; my own research on this subject is here). This literature includes papers by Robert Barro that imply that currency unions increase trade on a magical 10 fold basis, and a QJE paper which suggests that currency unions even increase growth. In my own eyes, the Euro has been a significant source of economic weakness for many European countries in need of more stimulative policies. (Aside from the difficulty of choosing one monetary policy for all, it also appears that MP has been too tight even for some of the titans of Northern Europe, including Germany. But that's a separate issue...)

Given my skepticism, I gave my sharp undergraduates at NES a seek-and-destroy mission on the Euro Effect on trade. Indeed, my students found that the apparent large impact of the Euro, and other currency unions, on trade is in fact sensitive to controls for trends, and is likely driven by omitted variables. One pointed out that the Glick and Rose estimation strategy implicitly assumes that the end of the cold war had no impact on trade between the East and the West. Several of the Euro countries today, such as the former East Germany, were previously part of the Warsaw Pact. Any increase in trade between Eastern and Western European countries following the end of the cold war would clearly bias the Glick and Rose (2017) results, which naively compare the entire pre-1999 trade history with trade after the introduction of the Euro.  Indeed, Glick and Rose assume that the long history of European integration (including the Exchange Rate Mechanism) culminating with the EU had no effect on trade, but that switching to the Euro from merely fixed exchange rates resulted in a magical 50% increase. Several of my undergraduates pointed out that this effect goes away by adding in a simple time trend control. Others noted that the authors only clustered in one direction, rather than in two or three directions one might naturally expect. In some cases, multi-way clustering reduced the t-scores substantially, although didn't seem to be critical. One student reasoned that the preferred regression results from GR (2017) don't really suggest that CUs have a reliable impact on trade. The estimates from different CU episodes are wildly different --  GR found that some CUs contract trade by 80%, while others have no statistically significant effect, some have a large effect, while others have an effect that is simply too large to be believed (50-140%). Many of my students noted that there is an obvious endogeneity problem at play -- countries don't decide to join or leave currency unions randomly -- and the authors did nothing to alleviate this concern. The currency union breakup between India and Pakistan is but one good example of the non-random nature of CU exits.

You'd think that a Ph.D.-holding referee for an academic journal which is still ranked in the Top 50 (Recursive, Discounted, last 10 years) might at least be able to highlight some of these legitimate issues raised by undergraduates. You might imagine that a paper which makes some of the errors above might not get published, especially if, indeed, star economists face bias in the publication system. You might also imagine that senior economists, tenured at Berkeley/at the Fed, might not make these kinds of mistakes which can be flagged by undergraduates (no matter how bright) in the first place. You'd of course be wrong.

The results reported and the assumptions used to get there are so bad that you get the feeling these guys could have gotten away with writing "Get me off your fucking mailing list" a hundred times to fill up space.

Before ending I should note that I do support peer review, and also believe that economics research is incredibly useful when done well. But science is also difficult. This example merely highlights that academic economics still has plenty of room for improvement, and that a surprisingly large fraction of published research is probably wrong. I should also add that I don't mean to pick on this particular journal -- if a big name writes a bad article, it is only a question of which journal will accept it. However, this view of the world suggests that comment papers, replications, and robustness checks deserve to be more valued in the profession than they are at present. Much of the problem with that line of work also stems from almost a willful ignorance of history. Thus, it's also sad to see departments such as MIT scale back their economic history requirements in favor of more math. I don't see this pattern resulting in better outcomes.

Update: Andrew Rose responds in the comments. Good for him! Here I consider each of his points.

Rose wrote: "-Get them to explain how that they could add a time trend to regression (2), which is literally perfectly collinear with the time-varying exporter and importer fixed effects."

Sorry, but a Euro*year interactive trend, or, indeed, any country-pair trend, is not going to even close to collinear with time-varying importer and exporter year fixed effects. The latter would be controlling for a general country trend, but not for trends in country-pair specific relationships. To be fair, regression of one trending variable on another with no control for trends is the most common empirical mistake people make when running panel regressions.

-Explain to them how time-varying exporter/importer fixed effects automatically wipe out all phenomena such as the effects of the cold war and the long history of European monetary integration.

Sorry, but that's also not the case. A France year dummy, to be concrete, won't do it. That would pick up trade between France and all other countries, including EU, EMU, and former Warsaw Pact countries. You'd need to put in a France*EU interactive dummy, for example. But such a dummy will kill the EMU. Below, I plot the evolution of trade flows over time (dummies in the gravity equation) for (a) all of Western Europe, (b) Western European EU countries, and (c) the original entrants to the Euro Area (plus Greece). What you can see is that, while trade between EMU countries was much higher before than after (your method), most of the increase happened by the early 1990s, in fact. Relative to 1998, trade even declined a bit. There's nothing here to justify pushing a 50% increase.

Rose also indicated that my undergraduates should "Read the paper a little more carefully. For instance, consider; and a) the language in the paper about endogeneity b) Table 7 which explicitly makes the point about different currency unions. "

Actually, let's do that. When I search for "endogeneity" in the article, the first hit I get is on page 8, where it is asserted that including country-pair fixed effects controls for endogeneity. Indeed, it does control for time-invariant endogeneity. But if countries, such as India and Pakistan, have changing relations over time (such as before and after partition), this won't help.

The second hit I get is footnote 7: "Our fixed‐effects standard errors are also robust. We do not claim that currency unions are formed exogenously, nor do we attempt to find instrumental variables to handle any potential endogeneity problem. For the same reason we do not consider matching estimation further, particularly given the sui generis nature of EMU." [the bold is mine.]

Actually, a correction here: my undergrads reported that the FE standard errors are actually clustered, but this is a minor point. You may not claim that currency unions are formed exogenously, but, as you admit, your regression results do nothing to try to reduce the endogeneity problem. And, this, despite the fact that I had already shared my own research with you (ungated version), which showed that your previous results were sensitive to omitting CU switches coterminous with Wars, ethnic cleansing episodes, and communist takeovers.

Also, the "For the same reason" above is a bit strange. The sentence preceeding it doesn't give a reason why you don't try to handle the endogeneity problem. The reason is? In fact, a matching-type estimator would be advisable here.

Lastly, in your discussion of Table 7, I see you note that it implies widely varying treatment effects of CUs on trade. But I like my undergraduates interpretation of this as casting doubt on the exercise. Many of the individual results, including an 80% contraction for some currency unions, are simply not remotely plausible. The widely varying results are almost certainly due to wildly different endogeneity factors affecting each group of currency unions, not due to wildly different treatment effects.

Thursday, April 13, 2017

Monday, April 10, 2017

A Quick Theory of the Industrial Revolution (or, at least, an answer to 'Why Europe?')

Following a Twitter debate involving myself, Gabe Mathy, Pseudoerasmus, and Anton Howes on the theory that high wages in England induced labor-saving technologies and led to the Industrial Revolution, I thought I should lay out my own quick theory on why the Industrial Revolution happened in Britain, or at least, why in NW Europe. In short, this theory is too speculative to write an academic paper about (plus, this theory is not popular with Economic Historians, so it wouldn't publish), and I don't have enough time to write a book. Twitter doesn't provide enough space, so a blog post it will be.

As far as we know, the high-wage economy that persisted in Europe after the Black Death was somewhat of an anomaly for the pre-Industrial world. Wages don't seem to have been as high in East Asia or India, while we actually don't know what wages were like in Africa. On the other hand, wages were even higher in many parts of the New World which had been recently depopulated, and where labor-land ratios were high. In any case, one can see the case for why economic agents would certainly try to cut back on high labor costs through new technologies. This theory has some sense, but I also see a few weaknesses. One is that "a wave of gadgets" swept over England at this time, with inventions including things like the flush toilet, which was not actually labor saving, and also the invention of calculus and of Malthusian economics. Also, many of the big technologies invented were actually quite simple, and so effective they would have been cost-effective to develop and implement at a wide range of relative prices/wages. A recent example of labor-saving technologies being worth it even for low labor costs is robots in low-wage China delivering mail.

Instead, I would focus on the other implication of high wages in a Malthusian world: fewer nutritional deficiencies, and higher human capital. This would include having consumers who can do more than simply buy necessities. High wages aren't enough, but rather I would think it's the size of human-capital adjusted population with which one is in contact with which will matter for technology growth. Thus, the Industrial Revolution could not have happened on a remote island with high wages, and would have been much less-likely in continents with North-South axis a la Jared Diamond. It also means that the rise of inter-continental trade would make overall technological growth faster, as technologies could be shared. This latter part of the story is probably crucial, as the rise of cheap American cotton was sure to be combined with the idea of mechanized textile factory production, especially since the latter had already been invented. (Indeed, one can't even produce cotton in England!)

The above logic could also answer why the IR didn't happen immediately after the Black Death. All I would argue is that if human capital is important for growth, then what we should expect to have seen after the BD in Europe is a relative "Golden Age" with a lot of progress and advance. In fact, the Black Death was the beginning of the end of the Dark Ages in Europe, as the Renaissance, the Age of Exploration, the Protestant Reformation, the Scientific Revolution, the Enlightenment, and the US Declaration of Independence all happened in the centuries thereafter. The printing press was invented in the 1450s in high-wage Germany. Modern banking was invented in Italy in the high-wage 1500s. Henry the Navigator had his formative years in the post-BD period of affluence in the 1410s. Brunelleschi discovered perspective in art in 1504. Newton invented the Calculus in the 1650s. The locus of technological change dramatically shifted to Europe -- before it had been a backwater. Europe then began colonizing the rest of the world. And, as it did, stagnant Eurasian agriculture imported a wealth of new agricultural technologies from the New World. However, I think it's better to view the Industrial Revolution not by itself as a special event, but as one of a long-line of major breakthroughs and accomplishments in the centuries after the Black Death, in which one sphere after another of European society was being transformed. Productivity soared in book-making after the introduction of the printing press, only there was much less elastic demand for books than there was for clothes and fashion, and so an Industrial Revolution could not depend on it. But the initial idea for mechanizing cotton textiles was probably not much larger or that much more difficult of a technological or intellectual breakthrough than these other revolutions, only it happened to be much more consequential in economic terms due to the nature of the industry.

The key difference between Europe and the rest of the world was that European cities and people were filthy, thus had high death rates which kept living standards high. This theory can also explain why "Not Southern Europe", as, for malthusian reasons, the post-Black Death high wages began to decline after around 1650 in the south. Note that this theory is also perfectly consistent with a cultural explanation for Britain's "wave of gadgets". A society in which half of the people suffer from protein deficiency is probably not going to be very vibrant culturally. Such a society may also develop institutions (the Inquisition) which place other barriers on development. Conversely, a society benefiting from high wages for Malthusian reasons might also be more likely to develop a culture and institutions conducive to economic growth.

In any case, this theory isn't completely new -- I've heard others, such as Brad DeLong, mention this as a possibility, but I haven't seen it explored in any detail. However, it won't be as popular with economists as the idea that growth is all about genetics. This idea was actually the first really big "Aha" moment I had after starting my Ph.D., as it popped right out of Greg Clark's excellent course on the Industrial Revolution, from where many of these ideas come. I eventually decided it was too speculative to write my dissertation on, so then switched to hysteresis in trade, and then to the collapse in US manufacturing employment. Maybe one day, post-tenure I'll return to growth...

Update: Pseudoerasmus points me to a very nice-looking paper by Kelly, Mokyr, and O' Grada, with a very similar theory to what I've written. They focus on England vs. France, and on the IR rather than everything which happened after the Black Death, and they don't appear to include Crosby-Diamond type effects, but I still approve.

Thursday, April 6, 2017

The Real Exchange Rates and Trade Literature

Noah Smith asks about the literature on the real exchange rate (RER) and trade.

My own main line of research is about RERs and manufacturing (also here on workers), RER measurement, and I've also done work on the impact of currency unions on trade, or lack thereof.

The first and third of these papers does include a bit on trade, although in neither case is it the focus. The third paper shows that the class of Weighted-Average Relative (WAR) exchange rates does a better job predicting US trade balances than do traditional indices. The difference is largely that the WAR indices reflect the impact of increased trade with the People's Republic of China. (In truth, the WARP index was first discovered by Thomas, Fahle, and Marquez in a very under-rated paper...)

I've also looked recently while prepping for class on a good paper on RERs and trade. In truth, the answer is that I also couldn't really find good, modern work that takes identification seriously (if you know of some, please add in the comments. Actually, when I began working on RERs and manufacturing employment, I could see that this literature had already become quite dated. Results were mixed, the best paper was still before the era in which standard errors were clustered in one direction much less two, each paper implied something different (of the four most recent using US data, one said RERs had only a small impact, a second said the impact depended on the specification, and a third said it had none, and a fourth said it was large), and the literature seemed to me in need of a modern treatment. However, I got a lot of pushback from the first time I presented this paper that the topic had "already been done". I think part of this stems from a certain gullability, and over-confidence among certain economists in their profession. If a paper is published in a good journal, then that's the end of the story. It must be true. Even if the paper was from 1991, and the results came from 600 data points and included few controls, and barely any robustness. In truth, I suspect that probably more than half of published research is straight wrong. In addition, much of what is "right" might offer incomplete evidence, or still has plenty of room for improvement. A perfect paper probably does not exist, and so I see papers that subject already published research results to new tests as being helpful, and quite worthy of publication in top field journals. (This is almost certainly a minority opinion...)

One thing I probably overlooked is simply that the literature on RERs and trade isn't that great. I'm still contemplating doing a paper on this, although I'm sure I'd have a lot of similar pushback. ("This result is not new.") The big issue in this literature is identification. In theory, the correlation between the RER and trade could go in either direction. That's because something like the Asian Financial Crisis could cripple the industrial (tradable) sector and also lead to a severe currency depreciation. Thus, the raw correlation between trade and the RER could be negative, positive, or zero in the aggregate. I haven't seen anyone really try to solve the identification problem here. (Well, OK, there was an economic history paper that looked at countries which pegged to gold vs. silver, and then what happened when the price of gold to silver changes, but what it seemed to me to miss was that this also had implications for monetary policy, and so wasn't quite exogenous.)

In any case, the end conclusion is that this is very much a literature in need of improvement.

Tuesday, April 4, 2017

Some International Data on Industrial Robots

Via Adam Tooze on Twitter.  The picture quality is poor, but here it is below. The US in fact has fewer robots than Germany and Japan, and yet manufacturing employment has fallen by more.

Sunday, April 2, 2017

The Gold Standard, the Great Depression, and the Brilliance of NES Students...

Tomorrow's lecture is, in part, covering a homework on the Great Depression in which the students were asked to redo some of a classic Bernanke and James article on the Great Depression. It's a great article, although the empirics -- like all empirics from the early 1990s -- are quite dated. This actually makes it good to assign, in my view, as it makes it relatively easy for students to suggest improvements. The first time I assigned this, I had a student (A.A.) who wasn't quite happy with the limited information contained in a regression of Industrial Production on gold standard status. Thus, she created this. It makes it clear, aside from the wonders of conditional formatting. There are two things this makes obvious: (1) the later you abandon the gold standard, the worse you did. And, (2) at first, if anything, the gold dead-enders were doing slightly better (or as well), but the further they went the worse they did. It blew my mind. Absolutely brilliant table for an undergraduate to turn in for a two page essay. Go back and have a look at the Bernanke/James tables and compare. There's no comparison. I have a feeling she, and many others I've had the good fortune to teach, will go on to do great things).