New publication: Ambient air pollution and non-communicable respiratory illness in sub-Saharan Africa: a systematic review of the literature
New publication from our Air Pollution and Health team out today in BMC Environmental Health:
Aerosol pollutants are known to raise the risk of development of non-communicable respiratory diseases (NCRDs) such as asthma, chronic bronchitis, chronic obstructive pulmonary disease, and allergic rhinitis. Sub-Saharan Africa’s rapid pace of urbanization, economic expansion, and population growth raise concerns of increasing incidence of NCRDs. This research characterizes the state of research on pollution and NCRDs in the 46 countries of Sub-Saharan Africa (SSA). This research systematically reviewed the literature on studies of asthma; chronic bronchitis; allergic rhinitis; and air pollutants such as particulate matter, ozone, NOx, and sulfuric oxide.
We searched three major databases (PubMed, Web of Science, and Scopus) using the key words “asthma”, “chronic bronchitis”, “allergic rhinitis”, and “COPD” with “carbon monoxide (CO)”, “sulfuric oxide (SO)”, “ozone (O3)”, “nitrogen dioxide (NO2)”, and “particulate matter (PM)”, restricting the search to the 46 countries that comprise SSA. Only papers published in scholarly journals with a defined health outcome in individuals and which tested associations with explicitly measured or modelled air exposures were considered for inclusion. All candidate papers were entered into a database for review.
We found a total of 362 unique research papers in the initial search of the three databases. Among these, 14 met the inclusion criteria. These papers comprised studies from just five countries. Nine papers were from South Africa; two from Malawi; and one each from Ghana, Namibia, and Nigeria. Most studies were cross-sectional. Exposures to ambient air pollutants were measured using spectrometry and chromatography. Some studies created composite measures of air pollution using a range of data layers. NCRD outcomes were measured by self-reported health status and measures of lung function (spirometry). Populations of interest were primarily schoolchildren, though a few studies focused on secondary school students and adults.
The paucity of research on NCRDs and ambient air pollutant exposures is pronounced within the African continent. While capacity to measure air quality in SSA is high, studies targeting NCRDs should work to draw attention to questions of outdoor air pollution and health. As the climate changes and SSA economies expand and countries urbanize, these questions will become increasingly important.”
New publication: “Long-Term PM2.5 Exposure Is Associated with Symptoms of Acute Respiratory Infections among Children under Five Years of Age in Kenya, 2014”
In early December, I was asked to submit a paper to a special issue on “Air pollution and health in Africa and the African Diaspora” which is great! But the deadline was Dec 31st, which is absolutely crazy. I pulled an amazing team together and somehow we made the deadline and now, here we are…. published!
Here’s the “video abstract.”
Introduction: Short-term exposures to air pollutants such as particulate matter (PM) have been associated with increased risk for symptoms of acute respiratory infections (ARIs). Less well understood is how long-term exposures to fine PM (PM2.5 ) might increase risk of ARIs and their symptoms. This research uses georeferenced Demographic Health Survey (DHS) data from Kenya (2014) along with a remote sensing based raster of PM2.5 concentrations to test associations between PM2.5 exposure and ARI symptoms in children for up to 12 monthly lags. Methods: Predicted PM2.5 concentrations were extracted from raster of monthly averages for latitude/longitude locations of survey clusters. These data and other environmental and demographic data were used in a logistic regression model of ARI symptoms within a distributed lag nonlinear modeling framework (DLNM) to test lag associations of PM2.5 exposure with binary presence/absence of ARI symptoms in the previous two weeks. Results: Out of 7036 children under five for whom data were available, 46.8% reported ARI symptoms in the previous two weeks. Exposure to PM2.5 within the same month and as an average for the previous 12 months was 18.31 and 22.1 µg/m3, respectively, far in excess of guidelines set by the World Health Organization. One-year average PM2.5 exposure was higher for children who experienced ARI symptoms compared with children who did not (22.4 vs. 21.8 µg/m3, p < 0.0001.) Logistic regression models using the DLNM framework indicated that while PM exposure was not significantly associated with ARI symptoms for early lags, exposure to high concentrations of PM2.5 (90th percentile) was associated with elevated odds for ARI symptoms along a gradient of lag exposure time even when controlling for age, sex, types of cooking fuels, and precipitation. Conclusions: Long-term exposure to high concentrations of PM2.5 may increase risk for acute respiratory problems in small children. However, more work should be carried out to increase capacity to accurately measure air pollutants in emerging economies such as Kenya.
New publication: An urban-to-rural continuum of malaria risk: new analytic approaches characterize patterns in Malawi
12 years in the making! Our new paper from partners at the University of Michigan and the #Malawi College of Medicine on new approaches to defining urban and rural environments in the context of malaria risk is now out in #Malaria Journal.
It was the last chapter in my dissertation to be published (all the rest were published when I was still in grad school.)Short version: malaria is complicated and really local. Malaria transmits poorly in urban and environments and well in rural environments. There’s urban like spaces in “rural” areas and rural-like spaces in “urban” areas, demanding a more nuanced view of what those terms really mean.
We know that malaria is a “rural” problem, but not all “rural” spaces are the same. Even in the country, there are “urban like” spaces and in “rural like” spaces even in the largest cities in Sub-Saharan Africa. Could those spaces impact malaria risk? If so, shouldn’t we redefine what we mean by urban vs. rural to inform intervention strategies to better target resources?
Here, we combine GIS and statistical methods with a house to house malaria survey in Malawi to create and test a new composite index of urbanicity and apply that to create a more nuanced risk map.
The urban–rural designation has been an important risk factor in infectious disease epidemiology. Many studies rely on a politically determined dichotomization of rural versus urban spaces, which fails to capture the complex mosaic of infrastructural, social and environmental factors driving risk. Such evaluation is especially important for Plasmodium transmission and malaria disease. To improve targeting of anti-malarial interventions, a continuous composite measure of urbanicity using spatially-referenced data was developed to evaluate household-level malaria risk from a house-to-house survey of children in Malawi.
Children from 7564 households from 8 districts in Malawi were tested for presence of Plasmodium parasites through finger-prick blood sampling and slide microscopy. A survey questionnaire was administered and latitude and longitude coordinates were recorded for each household. Distances from households to features associated with high and low levels of development (health facilities, roads, rivers, lakes) and population density were used to produce a principal component analysis (PCA)-based composite measure for all centroid locations of a fine geo-spatial grid covering Malawi. Regression methods were used to test associations of the urbanicity measure against Plasmodium infection status and to predict parasitaemia risk for all locations in Malawi.
Infection probability declined with increasing urbanicity. The new urbanicity metric was more predictive than either a governmentally defined rural/urban dichotomous variable or a population density variable. One reason for this was that 23% of cells within politically defined rural areas exhibited lower risk, more like those normally associated with “urban” locations.
I was just reading a transcript of Benjamin Bratton’s takedown of TED, the immensely popular series of talks on science and innovation. Perhaps the word “talk” is a bit too specific. TED is more of a “format” for presenting ideas.
To be clear, I think that having smart people who do very smart things explain what they doing in a way that everyone can understand is a good thing. But TED goes way beyond that.
Let me tell you a story. I was at a presentation that a friend, an Astrophysicist, gave to a potential donor. I thought the presentation was lucid and compelling (and I’m a Professor of Visual Arts here at UC San Diego so at the end of the day, I know really nothing about Astrophysics). After the talk the sponsor said to him, “you know what, I’m gonna pass because I just don’t feel inspired… you should be more like Malcolm Gladwell.”
At this point I kind of lost it. Can you imagine?
Think about it: an actual scientist who produces actual knowledge should be more like a journalist who recycles fake insights! This is beyond popularization. This is taking something with value and substance and coring it out so that it can be swallowed without chewing. This is not the solution to our most frightening problems — rather this is one of our most frightening problems.
I couldn’t agree more. As scientists, we are required to be able to explain our research to the outside world. Aside from the important matter of justifying our existence and use of public funds, some of us would hope that our work improves the world. However, the process of explaining shouldn’t involve unnecessarily dumbing down or overstating the potential impact of our work.
TED demands that every presentation be centered around some success. We have to end the talk on some positive note, proudly declaring that our work went the way we wanted it to and had a profound impact on the world. We are there to create, innovate and inspire.
The trouble is that science is often hardly creative, sometimes not innovative and often wholly uninspiring. Mind you, I don’t consider these to be negatives.
Much of science involved the testing of previously held results, views and conclusions. We aren’t seeking to create something new, but rather to evaluate the validity of what has been created before or commonly assumed. We are pursuing knowledge with the hope of refining how the world sees itself using methods to create hypotheses, gather evidence and rigorous test our assumptions.
The outcome, of course, is that the road of science is paved with failure. We embark on our adventures with money in hand, a plan, the proper tools and the best intentions, but, in most cases, we find out that the money didn’t go as far as we would have liked, the plan was ill-conceived given the realities on the ground, the tools were insufficient and our intentions may have been misplaced. At least, that’s my experience of science.
Again, I don’t see this as a negative. In order to improve our ability to understand the world and potentially ameliorate it’s problems, we are required to fail. A child can’t learn to walk without falling down. I can’t learn how to not offend people in Japanese without offending people more than a few times. I can’t learn how not to bake a cake without creating an inedible mess.
TED talks overlook this process of failure, focusing exclusively on the positives and the successes and, more troubling, the inspirational nature of the work. But then, this is a problem that’s not unique to TED talks. I find that TED talks are really just symptomatic of a broader trend which discourages negative results to the point where scientists troll the data hoping to find at least something that can be labelled “successful.”
Most journals won’t publish papers with negative results and most people don’t want to read them. To me, though, there is as much to learn from a paper which found that the previously held view was correct than one which refutes it. There is as much to know from a project which failed miserably as one which was “successful.” At least in my discipline, where field work under pressing circumstances is the norm, it would be nice to hear where people went miserably wrong. We could waste a lot less time, money and experience a little less frustration.
This success driven culture isn’t, of course, limited to science. It permeates our culture, particularly our children. This young generation (and their parents) appears wholly frightened of failure, potentially to the point of paralysis. If we aren’t careful, we might turn into the stagnant Japan of the 00’s.
TED talks probably have to go. While they worked well in the Gates era where small technological fixes in isolated boxes were thought to solve mankind’s most pressing problems, we need to move on to a format which effectively looks to the process of exploration. We need to know and accept that we will fail and those potential sources of failure need to inform our current strategies.
We need to integrate people of many disciplines for mutual benefit. For example, as a quantitative scientist, I learn a lot from people in the humanities, who often hold viewpoints and perspectives completely different from my own but no less important.
In short, we need more discussion and less posturing. Failure is good because we learn from it. Let’s not let the the scientific forum, as Dr. Bratton noted, becomes like cheap, inspirational, yet myopic and wholly useless megachurches.
Does malaria facilitate the development of exploitative agricultural estates? Interview with Dr. Luis Chavez
My friend Luis just published a paper in PlosOne on land consolidation or the formation of “latifundia” in Spain. Latifundia were large agricultural estates owned by the Romans, often dependent on slave labor, the growth of which has been implicated in Rome’s fall.
Luis creates a mathematical model to describe the formation of these large estates. He then tests the hypothesis that malaria transmission exacerbated the situation, by forcing land owners to sell cheaply to opportunistic land owners in less malarious areas.
Luis, an ecologist who works on issues of disease transmission (and all around great guy), is somewhat unique in the world of quantitative sciences. He took a few minutes to talk to me so that you can see why.
Who are you and what’s your background?
If you ask the japanese they might say: O gata no hen na gaijinsan. As to my academic background, I studied biology/parasitology as an undergraduate, then mathematical ecology for a M.Sc. and then was granted a Ph.D. in ecology and evolutionary biology (note: at the University of Michigan).
Nevertheless, I have always been interested in the humanities, especially history since it gives the best vantage point to understand the present. I grew up in a household where mixing things/topics was usual. Both my father and grandfather went to grad school, something unusual in Latin America, and since i was child lunch time talk was heavy on the side of human rights and solidarity, science and the need for change. When Nelson Mandela died i remembered that a lovely family activity during my childhood was going to a cultural/educational event in solidarity with Nelson Mandela and the South African people to end the apartheid.
For lay people, what’s the paper about and what motivated you to explore it?
The paper presents a mathematical model that can explain the formation of latifundia (large estates) when the profitability of land varies across landowners in a landscape. The model is also used to show that when such differences are not present latifundia still can emerge if there are differences in the risk of acquiring an infectious diseases. I built the model based on historical records to show that both patterns have been observed in societies as different as “latin” Europe (Italy and Spain) and China.
What’s a “latifundium” in Spain? I dug around a bit and could find some things about Rome and Latin America, but not so much about Spain. Why choose Spain?
A latifundium is a large estate, which requires the labor of people that do not own the land. I chose Spain because a essay by Chantal Beauchamp presented a couple of striking maps showing that places where malaria was common were those where Latifundia were common during the 1930s (Fig. 2): http://www.persee.fr/web/revues/home/prescript/article/ahess_0395-2649_1988_num_43_1_283483
The pattern of association between malaria and latifundia was not new, but only Beauchamp had data amenable for a quantitative analysis.
Are you trying to say that malaria helped enable capitalist land appropriation?
It might be the case. The hypothesis that malaria helped to enable land appropriation was put forward by the great italian malariologist, Angelo Celli. He has a book on the topic [reference 8 in the paper, available at the UMICH SPH library]. Celli was probably the most advanced malaria epidemiologist at the turn of the 20th century.
Unfortunately, he and other italians [most notably Grassi] were blackbolded in the Anglo-Saxon world because they threatened the ego of Ronald Ross by saying malaria was not just due to a parasite transmitted by the bite of a mosquito [a biological fact that, nevertheless, they independently showed and published in Italian]. If you are interested just check the oldest records for malaria in the Nature archives.
Though issues of land tenure are very different in the US (given that we killed all the natives and stole it all), we did have some big and awful land plantations in the South along with a serious malaria problem. Might we also try to apply this to the United States, and, if so, how?
I think it might have helped to the consolidation of large estates in the south. Interestingly in the Midwest you never had the latifundia observed in the south, but you had malaria in Michigan (the midwest) at some point (See Humphreys M. 2001. Malaria: Poverty, Race, and Public Health in the United States. Baltimore (MD): Johns Hopkins University Press.).
Nevertheless, in the south due, for example, to Jim Crow laws there might have been a differential risk of malaria infection not observed in the Midwest. However, i found no data to go beyond speculation, well other that in the Canal Zone the Jim Crow housing organization showed the differential malaria risk: http://www.jstor.org/stable/10.1086/529265
I find these quantitative approaches to historical problems fascinating (I also started work on a paper on malaria in post-conflict Angola, maybe I should publish it). Do you think applying these methods to history as informative to present day problems? If so, how?
I think so, history probably gives the best vantage point to understand the present (Rendering history a tinker damn’s is a good strategy to sell things no matter if they are useful or even safe, Henry Ford was clear about this). In theory failures can be highly educational, something the model suggests is that equity in land tenure is an unstable equilibrium that could only be maintained by an external policy as the Chinese did before the An Lushan rebellion, and that any kind of unfair land redistribution could only be expected to not work (latifundia will be eventually formed), as observed over and over in most Latin American nations.
The mix of methods is rather novel. However, in the discipline focused and partitioned environment of academia, do you find that its hard to get an audience for this kind of work? Is there a future in it?
I can tell you this stuff is only suitable for publication on the Arxiv.org or PLoS One/ Springer Plus, if you want it to be peer reviewed and you don’t sign your paper with an address in Princeton or Oxford. I think the audience does not belong in any department, though scholars working on the diverse fields of ecology, health, sociology, maths, economics and even history might find it interesting. I think there is some future, there is the emerging field of cliodynamics that looks at historical dynamics and there is even a journal for cliodynamics where they, every once on a while, publish good food for thought like this paper: http://escholarship.org/uc/item/1ks0g7dr#page-1
I thought my data was not dynamical enough, so I didn’t try there.
This work is heavily political. Do you think there is a place for politics in science?
I think everything gets embedded in politics. Otherwise there would have been no shutdown in the CDC and other US government agencies few months ago, etc. I don’t think my work is more or less political than a risk factor analysis for lung cancer and smoking. I think i might be blackbolded by some of the references I cited, but to understand Capitalism even the Catholic Church is studying Marx [Funny the leading scholar is the Munich Bishop, whose last name is Marx]:
For those keeping up, you may remember that I spent the summer in Kenya, working with a team extracting blood samples from camels, cows, goats and sheep. We were in contact with all of these animals on almost a daily basis. We weren’t wearing any protection at all, but it’s inconceivable to wear a full hazmat suit while taking blood from goats in a Maasai community. You’d get laughed out of town.
My days right now are running in a fairly predictable pattern. I wake up, feel pretty good, eat breakfast and drink some coffee. At about 10-11 a.m. I begin to feel dizzy, sweat somewhat, a low grade fever kicks in and a horrible taste develops in my mouth. My peripheral vision is limited and I have trouble focusing on distant objects. It gets progressively worse throughout the day, but improves before dinner. After dinner, I feel worse than before. I’m positive that the brunt of the physical symptoms are associated with anemia. It’s like a low grade malaria.
The psychological effects are fascinating. Again, in the morning, I feel fine. As the day progresses, I am less and less able to string coherent sentences together (not that I’m good at it in the best of times), lose thoughts in mid sentence and can’t remember important vocabulary words. I’m stuck in an existential funk where the thought of tomorrow is dark, I’ve forgotten the past and the present isn’t all that meaningful. I often find myself staring into space and time passes quickly.
Though I have no other negative physical effects and am able to leave the house and move around, I’m finding this incredibly debilitating. Even writing this blog post is a challenge.
From the pathogen’s standpoint, this situation is ideal. It doesn’t immediately kill the host, and the bacteria tends to incubate in cells so that it can avoid the body’s immune response. If I were a herd animal, eating and defecating in the same space, I would be able to transmit for, conceivably, the rest of my life. The low grade anemia keeps the animal mobile, yet impedes its ability to evade predators, allowing transmission to occur from herbivorous ungulates to carnivorous animals.
Again, because the bacteria hides out in cells, it’s a bear to kill. I have two months of two types of antibiotics to look forward to, both with different schedules and dietary requirements. One causes awful nightmares (doxycycline).
If left untreated brucellosis can include abscesses in the joints, spinal problems, blindness and inflammation of the testicles. It is anecdotally associated with elevated rates of suicide in veterinarians. I’m wondering how much chronic brucellosis there is in pastoralist communities in Sub-Saharan Africa. The burden must be quite severe.
This is going to be rough, but it’s better than a lifetime of these symptoms. I’m certainly finding this scientifically interesting, though I will be happy to have it gone for good.
I think that rather than ask whether humans are “more important than other species,” we have to explore the human-nature dichotomy itself. Unfortunateley, discussions on environmental issues seem to start from an assumption that one exists. These discussions, which put humans at odds with nature, generally lose me on three points (though, again, this is not my field of expertise):
1) The intense focus on large mammals. If we are going to convince ourselves that “nature’s” needs are more important than our own (or simply worth considering) we have to eliminate the idea of a hierarchy of species and consider all living things as equally important. It often seems that conversations become less holistic and more mammal-centric. Given that we are mammals and hard wired to like cute and furry things (particularly those small and weak), this is to be expected. However, the urge to protect things like ourselves makes it impossible for humans to objectively rank the importance of living things.
How often do you hear about people screaming to save snakes? Perhaps it happens and I just don’t hear about it. Clearly, big furry animals are an easy sell.
2) The idea that “species” are distinct entities, the number of which needs to be maximized at any cost. Preserving more species is seen as a goal, when in fact, the word itself is not uncontroversial. “Species” is a rough and artificial concept created by humans to assist in our understanding of the world. Even scientists can’t agree on what a species is, given that the situation that determines how a species is defined differs by type of animal and context (and history).
Take the Zebra, which comes in three main flavors, though I’ll focus on two. The Grevy zebra is Equus grevyi and the plains zebra is Equus quagga, different “species” by classification, but able to breed with one another and create offspring which are able to reproduce. The two “species” are distinct from one another only in superficial morphological features (stripes and size) and behavior.
Gravy’s, though genetically indistinct from plains zebras, are listed as endangered, which gives them certain benefits and allows Kenya (for example) to legally restrict grazing for Maasai goat herders, with the support of international groups. It’s a simplistic example, but it makes little sense to me to ask that humans make sacrifices based on a flawed concept of what makes a “species.” It also makes little sense to create policy which impacts the lives of Africans based on a false paradigm created by 19th century Europeans (“Gravy” was a French President). Yet, here we are.
An aside, but I often think that people really believe that “species,” particularly large mammals, are individuals with distinct personalities and collective thought patterns. From the animals’ standpoint, extinction isn’t an issue. Rhinos don’t hold regular meetings and worry collectively about extinction. Individual rhinos are merely concerned with eating enough grass and mating when necessary.
3) The concept that nature is a fragile and static entity which would be ultimately benefit from our non-existence. This stems from traditional dichotomies of “man” and “nature” where man operates in his (male) world and nature operates in an entirely separate and unchanged sphere. In the West, this goes all the way back to Genesis. It is a simplistic and useless concept and does more harm than good.
Nature is a dynamic and constantly changing system of which we are one part. We create nature “reserves” which are thought to “preserve” the “natural” state of “nature” but even these are artificial, human constructed spaces, as we have dictated the location and killed all our large wildlife. We approach them are “preserves”, but forget that we have altered the system (by, for example killing the wolves or cutting all the pine trees in Michigan). Thus, arguing for the “preservation” of nature is somewhat disingenuous, since even by advocating for what part of nature needs to be preserved, we are writing its rules.
The question of whether the world would be better or worse off without us is fairly moot since humans are defining the terms of “better” and “worse.” Moreover, from the German cockroach’s (Blattella germanica) standpoint or the Black rat (Rattus rattus), humans could be considered a great thing as we tend to migrate and take our pests with us. If it could, Plasmodium falciparum should worship us like a God, since it wouldn’t exist without us.
I don’t see man as separate from nature. For better or for worse, we are a part of it. But after we have run our course, the world will go on without us. “Nature,” however it may be defined, has shown itself to be a tough beast in the past. Even if the entire planet became desertized (is that a word?), life would continue to exist. One day, with or without us, all life on Earth will cease to exist.
The most salient questions should revolve around how our environmental impacts affect our long term survival for humans. Focusing on our own needs is the only sustainable strategy (though I despise the word).
Policy makers in the US and Europe seized on the paper as proof that cutting stimulus and social programs was a good idea, and proceeded to do so with abandon. Of course, right wingers wanted to cut money to social programs anyway, and would have done so regardless, but the paper was held out as scientific proof that it was a solid plan of action.
I won’t comment on how strange it was that Republicans were interested in science at all, given recent efforts to politicize the NSF and micromanage the grant decision process.
The trouble was that the results presented in RR were shown to be based on the selective use of data. Thomas Herndon, a 28-year-old graduate student, obtained the dataset from RR themselves and couldn’t reproduce the results.
In fact, he found that the only way to accurately reproduce the results in RR’s paper that showed that high debt restrained economic growth was to exclude important cases. When including the missing data, high debt was associated with consistently positive growth, though modestly slowed.
Originally, I took the view that this was a case of sloppy science. RR had a dataset, got some results which fit the narrative they were pushing and didn’t pursue the matter any further. Reading Herndon’s paper, however, I changed my mind.Herdon took the data and did what any analyst would do when starting exploratory analysis, he plotted it (see figure on the right). Debt to GDP ratios and growth are both continuous measures. We can do a simple scatterplot and see if there’s any evidence that would suggest that the two things are related.
To me, this is a pretty fuzzy result. Though the loess curve (an interpolation method to illustrate trend) suggest that there is *some* decline in growth overall, I’d still ding any intro stats student for trying to suggest that there’s any relationship at all. There is no way that RR, both trained PhD’s and likely having the help of a paid research assistant, didn’t produce such a plot.
Noting that the loess curve drops past approximately 120%, I calculated the median growth for each country represented. Only 7 countries have had debt to GDP ratios greater than 120% in the past 60+ years: Australia, Belgium, Canada, Japan, New Zealand, the UK and the United States. Out of these only two had (median) negative growth: Belgium (-.69%, effectively zero) and the United States (-10.94%), which has only had a debt to GDP greater than 120% one time. All other countries has positive growth under high debt, even beleaguered Japan. New Zealand can even claim a strong 9.8% growth under high debt. The US, then, is a major outlier, possibly bringing the entire curve down.
As this doesn’t fit their story, RR’s solution was to categorize debt to GDP ratios into five rough classifications, and calculate the mean growth within each group. This is a common trick to extract results from bad data. It’s highly tempting for researchers (and epidemiologists do it far too often), but a bad idea to present it without all the caveats and warnings that should go with it.
I’m not surprised that ideologues such as RR would be so keen to produce the result they did. After all, they published the popular economics work “This Time Is Different: Eight Centuries of Financial Folly” where they try to suggest that budget policy of the US in 2013 should somehow be informed by the economy of 14th century Spain.
I am, however, surprised that reviewers let this pass. If I would have been a reviewer, I would have:
1) pointed out the problems of categorization, where data doesn’t require it
2) noted that categorizing the data (or even plotting it) tears out temporal correlation. For example, one data point from 2008 (stimulus) may be put in the high debt category, but another from 2007 (crash) in the low debt category. While budgets of one year may have little to do with the budget of another, the economy of one year is likely related to the economy of the previous year.
3) questioned the causal mechanisms behind debt and growth. This is obviously a deep question for economists (and not epidemiologists), but of particular import. When does the economy start to react to debt? I’m pretty sure that there is a lag effect as spending bills tend to space disbursements over the course of the fiscal year.
The RR debacle should be a lesson, not only to economists, but to all scientists. While we may always be under pressure to produce results and hope that those results fit and support whatever position we take, shoddy methods don’t get us off the hook. In RR’s case, I would call this fabrication. A good many studies are merely guilty of wishful thinking, but the chance always exists that someone will come out of the woodwork and expose our flaws. After all, that’s what science is all about.
A couple of weeks ago, I attended a lecture on network analysis where the investigators analyzed popular political books on Amazon.com.
Amazon lists not only information on the book but also the titles, in order of purchasing frequency, of other books that customers may have purchased. The researchers here were able to identify left leaning and right leaning books by examining the purchasing habits of Amazon customers.
Decibel “is America’s only monthly extreme music magazine” and has been in publication since 2004. Every year, they publish the titles of the 40 best metal records of the year, according to their review staff.
Here is 2012’s list:
40 Gojira – L’Enfant Sauvage
39 Meshuggah – Koloss
38 Agalloch – Faustian Echoes EP
37 The Shrine – Primitive Blast
36 Incantation – Vanquish In Vengeance
35 Samothrace – Reverence To Stone
34 Devin Townsend Project – Epicloud
33 Panopticon – Kentucky
32 Saint Vitus – LILLIE: F-65
31 Mutilation Rites – Empyrean
30 Author & Punisher – Urus Americanus
29 A Life Once Lost – Ecstatic Trance
28 Asphyx – Deathhammer
27 Farsot – Insects
26 Gaza – No Absolute For Human Suffering
25 Inverloch – Dark/Subside
24 Swans – The Seer
23 Horrendous – The Chills
22 Killing Joke – MMXII
21 Early Graves – Red Horse
20 Liberteer – Better To Die On Your Feet Than Live On Your Knees
19 High On Fire – De Vermis Mysteriis
18 Napalm Death – Utiltarian
17 Torche – Harmonicraft
16 Grave – Endless Procession Of Souls
15 Satan’s Wrath – Galloping Blasphemy
14 Testament – Dark Roots Of Earth
13 Cattle Decapitation – Monolith Of Inhumanity
12 Blut Aus Nord – 777: Cosmosophy
11 Municipal Waste – The Fatal Feast
10 Pig Destroyer – Book Burner
09 Paradise Lost – Tragic Idol
08 Royal Thunder – CVI
07 Enslaved – Riitiir
06 Neurosis – Honor Found In Decay
05 Pallbearer – Sorrow and Extinction
04 Witchcraft – Legend
03 Evoken – Atra Mors
02 Baroness – Yellow & Green
01 Converge – All We Love We Leave Behind
I looked all of these records on Amazon. For each of them, I noted which of the others were in the first 12 titles that were purchased with it, creating a 40 by 40 adjacency matrix where rows (i) and columns (j) represented records. For each entry, a zero was noted where the customer which purchased the i-th record did not purchase the j-th record, and a one where they did.
I found that many of the records on the list were purchased with one another. The most common record purchased in combination with another on the list was Neurosis‘ “Honor Found in Decay.” Fifteen of the other records on this Top 40 were purchased with “Honor Found in Decay.”
In network terms, the Degree of this record would be 15. Pallbearer’s “Sorrow and Extinction” had a degree of 11, Royal Thunder’s “CVI” and Blut Aus Nord’s “777: Cosmosophy” both had a degree of 9.
The network of Decibel’s Top 40 looks like this:
You can see that some records get purchased with other records more than others. The size of the dots represent the degree of the record.
Now, I did some cluster analysis on the data, looking for related groups of records within the network. Using R, I produced the following dendrogram:
There are two major clusters, each with its own subcluster (dendrograms are hierarchical). One includes Converge, Neurosis, Pallbearer Royal Thunder, Evoken and Inverloch with a subcluster including only the first four. These are all bands that might be expected to be purchased with one another. The other big one includes all the rest. Main clusters are designated by color.
I found one containing the three entries for Baroness, Municipal Waste and Napalm Death, very different bands. I’m truly not sure why those three would be in a cluster together (is the cluster is based on lonliness in the network?).
Anyway, I’m done, but glad I got any results at all. I’ll let readers (especially metal fans!) interpret the results.