Author Archives: rdmyers75@hotmail.com

social network theory and research

Here is a long paper with a lot of references on social network theory and empirical evidence, including learning and diffusion of innovations. For example,

A nice example of this using field data is a study of social learning by Conley and Udry (2001, 2004). They examine the use of fertilizer by pineapple farmers. In particular, they show that changes in the amount of fertilizer used by a given farmer are related to the success or failure of similar past changes in fertilizer use by other farmers. Having controlled experiments can substantially narrow down the range of explanations for observed peer correlations. For example, Hesselius, Johansson, and Nilsson (2009) examine absences in the workplace based on a randomized rule affecting about 3000 workplaces in G oteborg Sweden. Randomly
assigned agents were allowed to have longer spells of absence from work (14 days) without having to produce a doctor’s certificate than was the rule for the general population (8 days). This resulted not only in an increase in absences for the treated individuals (those allowed the extra time before producing a doctor’s certificate), but also for non-treated individuals conditional on being in a workplace with many treated individuals. Interestingly, the affect of how many other treated individuals there were in the workplace did not significantly influence treated individuals’ behavior. This allows them to distinguish between various ways in which the peer effects might work, ruling out things like enjoying time together and being more consistent with a fairness effect or related peer effect on preferences. This sort of study shows the power of (field) experiments in identifying peer effects…
The list of settings where peer effects, or network effects more generally, have been found to be important is a long and varied one. It includes a range of things from criminal behavior (Reiss (1980), Glaeser, Sacerdote and Scheinkman (1996), Kling, Ludwig and Katz (2005), Patacchini and Zenou (2008)), to education (e.g., Calvo-Armengol, Patacchini and Zenou (2008)), to risk-sharing and loan behavior (Fafchamps and Lund (2003), De Weerdt (2004), Karlan, Mobius, Rosenblatt, Szeidl (2009)), to obesity (Christakis and Fowler (2008), Fowler and Christakis (2008), and Halladay and Kwak (2009)). (See Fafchamps (This volume), Ioannides (This volume), Jackson and Yariv (This volume), Munshi (This volume), Sacerdote (This volume), and Topa (This volume), for more examples and background on empirical evidence.)

Paul Romer and “mathiness”

Paul Romer has attacked a number of fellow economists for relying on what he calls “mathiness” rather than mathematical theory. He believes the study of economic growth and its practical applications have suffered because of this.

Academic politics, like any other type of politics, is better served by words that are evocative and ambiguous, but if an argument is transparently political, economists interested in science will simply ignore it. The style that I am calling mathiness lets academic politics masquerade as science. Like mathematical theory, mathiness uses a mixture of words and symbols, but instead of making tight links, it leaves ample room for slippage between statements in natural versus formal language and between statements with theoretical as opposed to empirical content.

Solow’s (1956) mathematical theory of growth mapped the word “capital” onto a variable in his mathematical equations, and onto both data from national income accounts and objects like machines or structures that someone could observe directly. The tight connection between the word and the equations gave the word a precise meaning that facilitated equally tight connections between theoretical and empirical claims. Gary Becker’s (1962) mathematical theory of wages gave the words “human capital” the same precision and established the same two types of tight connection—between words and math and between theory and evidence. In this case as well, the relevant evidence ranged from aggregate data to formal microeconomic data to direct observation…

The market for mathematical theory can survive a few lemon articles filled with mathiness. Readers will put a small discount on any article with mathematical symbols, but will still find it worth their while to work through and verify that the formal arguments are correct, that the connection between the symbols and the words is tight, and that the theoretical concepts have implications for measurement and observation. But after readers have been disappointed too often by mathiness that wastes their time, they will stop taking seriously any paper that contains mathematical symbols. In response, authors will stop doing the hard work that it takes to supply real mathematical theory. If no one is putting in the work to distinguish between mathiness and mathematical theory, why not cut a few corners and take advantage of the slippage that mathiness allows? The market for mathematical theory will collapse. Only mathiness will be left. It will be worth little, but cheap to produce, so it might survive as entertainment.

MERS in South Korea

“Middle East Respiratory Syndrome” has popped up in South Korea.

A deadly virus with no known cure — Middle East Respiratory Syndrome, or MERS — has infected 13 people in South Korea since mid-May. The fast spread of the disease, from the first case confirmed on May 20 to more than a dozen by Saturday, is prompting criticism of health officials for not moving faster to quarantine suspected patients…

MERS is from the same family as the virus that triggered China’s 2003 outbreak of Severe Acute Respiratory Syndrome, or SARS. Scientists first identified it in 2012, and since then, more than 1,100 cases have been reported in 23 countries, with the bulk majority of cases occurring in the Middle East.

So far, not only is there no known cure, there’s no vaccine to prevent it, either.

doubling of El Nino

Nature Climate Change says El Nino frequency could double due to climate change. The result: “severely disrupted global weather patterns, affecting ecosystems4, 5, agriculture6, tropical cyclones, drought, bushfires, floods and other extreme weather events worldwide3, 7, 8, 9”

El Niño events are a prominent feature of climate variability with global climatic impacts. The 1997/98 episode, often referred to as ‘the climate event of the twentieth century’1, 2, and the 1982/83 extreme El Niño3, featured a pronounced eastward extension of the west Pacific warm pool and development of atmospheric convection, and hence a huge rainfall increase, in the usually cold and dry equatorial eastern Pacific. Such a massive reorganization of atmospheric convection, which we define as an extreme El Niño, severely disrupted global weather patterns, affecting ecosystems4, 5, agriculture6, tropical cyclones, drought, bushfires, floods and other extreme weather events worldwide3, 7, 8, 9. Potential future changes in such extreme El Niño occurrences could have profound socio-economic consequences. Here we present climate modelling evidence for a doubling in the occurrences in the future in response to greenhouse warming. We estimate the change by aggregating results from climate models in the Coupled Model Intercomparison Project phases 3 (CMIP3; ref. 10) and 5 (CMIP5; ref. 11) multi-model databases, and a perturbed physics ensemble12. The increased frequency arises from a projected surface warming over the eastern equatorial Pacific that occurs faster than in the surrounding ocean waters13, 14, facilitating more occurrences of atmospheric convection in the eastern equatorial region.

climate change impacts

Here are a couple projections of climate change impacts.

The World Health Organization projects “Between 2030 and 2050, climate change is expected to cause approximately 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress.” This sounds awful, and of course it is. But if you compare this to other preventable causes of death like traffic accidents, smoking and air pollution, you could probably save a lot more lives with a given amount of money focusing on the latter group than exclusively on climate change.

A more sobering projection, at least to me, comes from an organization called DARA.  Although the report includes some truly awful and incomprehensible infographics, there is a very clear graphic on p. 21. Under a “no action” scenario, climate change subtracts about 3% from world economic growth in 2050 and 7-8% in 2100. If you believe technology will lead to a massive acceleration of economic growth, we may be able to afford even this (although our children will be learning about Earth’s original native ecosystems in history class). If long-term growth stays in the sub-5% range where it has been recently, this will mean the decline and fall of civilization as we know it.

growing the urban forest

This abstract in Restoration Ecology contains an interesting result: planting shrubs along with urban trees helps the trees. You might think the opposite, due to competition, but I have heard this before. One theory I’ve heard is that shrubs help establish beneficial fungi in the soil that pave the way for healthy trees. It shouldn’t be too surprising, when this is exactly the succession that will occur in an abandoned field over time, given enough rainfall and not too much fire.

Compost also helps trees, which might be surprising to some professional engineers but not to any amateur gardener (luckily, some of us are both!). Still, in urban stormwater management we engineers are often encouraged to plant trees and other vegetation, but to minimize organic matter because the same nutrients that trees need can become water pollutants if they find their way downstream. It’s a delicate balance. Civil, “environmental”, and geotechnical engineers aren’t good at finding it because it is not part of our typical training. We need the agriculture, forestry, and soil science types to help us with this.

Forests are vital components of the urban landscape because they provide ecosystem services such as carbon sequestration, storm-water mitigation, and air-quality improvement. To enhance these services, cities are investing in programs to create urban forests. A major unknown, however, is whether planted trees will grow into the mature, closed-canopied forest on which ecosystem service provision depends. We assessed the influence of biotic and abiotic land management on planted tree performance as part of urban forest restoration in New York City, U.S.A. Biotic treatments were designed to improve tree growth, with the expectation that higher tree species composition (six vs. two) and greater stand complexity (with shrubs vs. without) would facilitate tree performance. Similarly, the abiotic treatment (compost amendment vs. without) was expected to increase tree performance by improving soil conditions. Growth and survival was measured for approximately 1,300 native saplings across three growing seasons. The biotic and abiotic treatments significantly improved tree performance, where shrub presence increased tree height for five of the six tree species, and compost increased basal area and stem volume of all species. Species-specific responses, however, highlighted the difficulty of achieving rapid growth with limited mortality. Pioneer species had the highest growth in stem volume over 3 years (up to 3,500%), but also the highest mortality (up to 40%). Mid-successional species had lower mortality (<16%), but also the slowest growth in volume (approximately 500% in volume). Our results suggest that there will be trade-offs between optimizing tree growth versus survival when implementing urban tree planting initiatives.

air pollution and diabetes

Here is a long article citing evidence that air pollution is at least correlated, and quite possibly a contributing factor, to diabetes. The website is called diabetesandenvironment.org, so I don’t know if it is an unbiased source of scientific information. The scientific studies it cites are certainly real.

These authors suggest that oxidative stress, which involves an excess of free radicals, might be one mechanism whereby air pollutants could influence the development of type 1 diabetes. Ozone and sulfate can have oxidative effects. Particulate matter carries contaminants that can trigger the production of free radicals as well as immune system cells called cytokines (involved in inflammation), and may affect organs that are sensitive to oxidative stress (MohanKumar et al. 2008). Beta cells are highly sensitive to oxidative stress, and free radicals are likely to be involved in beta cell destruction in type 1 diabetes (Lenzen 2008)…

The children of mothers exposed to higher levels of air pollution while pregnant have a higher risk of later developing type 1 diabetes. This finding comes from the relatively unpolluted area of southern Sweden, and was found for both ozone and nitrogen oxides (NOx) (Malmqvist et al. 2015)…

A number of long-term studies have found that exposure to traffic-related air pollution is associated with an increased risk of type 2 diabetes in adults. For example, a study of African-American women from Los Angeles found that those who had higher exposure to traffic-related air pollutants (PM2.5 and nitrogen oxides) were more likely to develop diabetes (as well as high blood pressure) (Coogan et al. 2012). Adults in Denmark had an increased risk of diabetes when exposed to higher levels of the traffic-related air pollutant nitrogen dioxide (NO2)– especially those who had a healthy lifestyle, were physically active, and did not smoke– factors that should be protective against type 2 diabetes (Andersen et al. 2012). A study of adult women in West Germany found that women exposed to higher levels of traffic-related air pollution (NO2 and PM) developed type 2 diabetes at a higher rate. This study followed the participants over a 16 year period (at the beginning, none had diabetes) (Krämer et al. 2010). A long-term study from Ontario, Canada, found that exposure to PM2.5 was associated with the development of diabetes in adults (Chen et al. 2013). From Switzerland, a 10 year long study found that levels of PM10 and NO 2were associated with diabetes development in adults, at levels of pollution below air quality standards (Eze et al. 2014).

So does it make sense that we are obsessing over chemicals like trace agricultural pesticide residues in food and “microconstituents” in drinking water, rather than air pollution, which is 100% proven to be extremely harmful? I am not suggesting that we shouldn’t be concerned about all of the above, but in a world of finite resources and time we should calibrate our amount of concern and action to the biggest, most proven risks, while continuing to learn more about the others. The internal combustion engine is killing us and our children, slowly through the air not to mention through sudden, violent death on the ground.

A few more interesting air pollution notes:

  • China may have reached peak coal, with its consumption actually falling last year. World energy consumption has been known to fall during recessions, but this is supposedly the first time it has fallen during an economic expansion. The economics of renewables seem to be playing a significant role.
  • Air pollution kills more people worldwide than tobacco.
  • A Chinese documentary about air pollution called “Under the Dome” was seen by 300 million people in less than a week before it was censored in China. The film maker was partly inspired by a rare tumor her daughter developed in the womb that she links back to air pollution.
  • Confusingly, Under the Dome was also the title of a recent Stephen King novel and TV series. In Stephen King’s 1982 novel The Running Man, which he wrote under the pseudonym Richard Bachman, children are dying right and left of emphysema and cancer caused by air pollution. The government is covering it up and keeping people distracted and entertained with reality TV shows.

green roofs

Everybody kind of likes the idea of green roofs, but water professionals are not always 100% confident we understand them well enough to promise they will meet water quality and flooding regulations. But the studies are gradually trickling in. Here is a new one from Ecological Engineering:

Increasing recognition is being given to the adoption of green roofs in urban areas to enhance the local ecosystem. Green roofs may bring several benefits to urban areas including flood mitigation. However, empirical evidence from full-scale roofs, especially those that have been operational for more than several years is limited. This study investigates the hydrologic performance of a full-scale extensive green roof in Leeds, UK. Monitoring of the green roof took place over a 20 month period (between 30th June 2012 and 9th February 2014). The results indicate that the green roof can effectively retain and detain rainfall from the precipitation events included in the analysis. Retention was found to correspond significantly with rainfall depth, duration, intensity and prior dry weather period. Significant differences in retention values between the summer and winter seasons were also noted. Regression analysis failed to provide an accurate model to predict green roof retention as demonstrated by a validation exercise. Further monitoring of the green roof may reveal stronger relationships between rainfall characteristics and green roof retention.

Beyond questions on performance, there is a kind of chicken and egg problem where they are not used much (in the U.S., at least) because they are expensive and they are expensive because they are not used much. That is true of many emerging technologies. Of course, this “emerging” technology has been used in Europe for centuries, not to mention it is also popular with hobbits.

robots

Here’s a robot learning some tasks on its own. It’s interesting that my two year old human child is roughly around this same stage – he has thoroughly mastered a couple of these tasks, like putting a ring on a stick or a peg in a hole. He is still getting the hang of others, like sticking together legos and screwing on a lid. He has other skills though that I doubt the robot has, like making fart jokes and flirting with pretty girls (which sometimes go together at this age).

Robert Reich vs. Amanda Ripley

Interesting ideas. Free college, free child care, and universal health care are the kinds of bold ideas we need to be talking about to build a resilient 21st century economy.

I recently read The Smartest Kids in the World and How They Got That Way by Amanda Ripley. I liked the book because although it followed a plot of human interest and anecdote to keep the reader engaged, it had a hard core of data underneath. Data doesn’t always lead you down the path you expect, and sometimes it doesn’t tell you what you want to hear. For example, there is no clear evidence that better outcomes are linked to teacher pay, class size, or funding levels, three of the policies Robert Reich advocates above. What seems to make a difference is very high expectations of both teachers and students. Finland for example closed most of its teacher colleges, moved the few remaining into a few elite universities, and made them hard to get into and hard to successfully complete. Those who successfully complete them do get paid well, but there are other countries like Spain and Norway that also pay teachers well and don’t have nearly as good outcomes. High expectations can also come from parents, but they have to be academic expectations. Parental involvement is not that helpful if it is focused on sports and activities other than academics. Parental involvement outside of school, such as reading, is also very, very important. You come away from the book kind of scratching your head about how important school really is and whether any of it is really under your control as a parent, but at least you know the factors outside of school are important and under your control.