Published by EH.Net (August 2012)

Response to John Murray?s review of Parasites, Pathogens, and Progress: Diseases and Economic Development — by Robert A. McGuire and Philip R. P. Coelho.

We feel obligated to comment on John E. Murray?s review (EH.Net, May 2012, of our book, Parasites, Pathogens, and Progress: Diseases and Economic Development (Cambridge, MA: MIT Press, 2011) because we are puzzled with what Murray wrote.? His review inaccurately portrays the book?s contents, evidence, and hypotheses.? The review was ?bad? in the sense that it neither informed the reader what the book was about nor did it accurately describe the book.? It was not ?bad? because it panned our book, but because the review gave little information about major aspects of what was actually in the book.? Many of the criticisms were erroneous or misleading.? More egregiously, in a number of instances the review contained factual inaccuracies.

There are a number of strands in Parasites, Pathogens, and Progress.? Among them are (1) an attempt to integrate the impact of infectious diseases into the physical and social evolution of humanity starting from around 200,000 years ago, (2) a critique of the Malthusian theory of population, arguing that diseases caused the poverty and misery that Malthus ascribed to over-population, (3) an economic analysis of the interactions of African slavery, including financial analysis and data that suggest that diseases were the key factor in the promotion and preservation of slavery in the American South, (4) an economic history of the regional impacts of diseases in the New World and their importance in American history prior to the twentieth century, and (5) a substantial amount of empirical evidence (mortality rates for various age and other cohorts for about two dozen infectious diseases) on the regional incidence of diseases in the United States during the nineteenth century.? What Murray says about our book is almost a caricature, claiming it is primarily about malaria, and what we say everyone knew except for the parts that are incorrect.

Among the notable absences from the review is our history of humanity (chapter 2) that emphasizes population growth, expanding markets, evolutionary theory, and Malthusian Doctrine; Murray does not mention these.? Murray does have a sentence about chapter 3: ?On the purely economic side, a set of verbal and flowchart models of economic growth stress connections between ever greater population density and increasing infectious disease rates.? Perhaps Murray thought that an entire chapter offering models of pre-modern long-run economic growth focusing on population growth, expanding markets, increasing specialization, increasing density and urbanization, and transportation developments, and the consequent spread of pathogens did not deserve further comment; we disagree.? If we are wrong in chapter 3, this is a major error and should be pointed out; but if we are correct, then it is a significant contribution.? While his review does acknowledge our hypothesis about slavery versus indentured servitude and differential disease susceptibilities, Murray completely neglects our formal analysis of slavery versus indenture servitude (and by extension the use of African versus European labor) in early America (chapter 4).? Our analysis depends on financial and microbiological considerations and includes evidence on prices, interest rates, life expectancies/length of service, and the net returns necessary for a slave or a servant to be profitable in early America.? Finally, Murray neither mentions the evolutionary theory that is critical to our view of humanity?s history and the economy, nor does he mention our claim that Malthus was wrong (chapter 2), but that Malthus had an intuition associating increased human density with poverty (chapter 3).? A criticism that Murray does not make is the absence of sufficient evidence to overthrow the Malthusian Paradigm; the lack of specific data and empirical tests would have been a legitimate criticism.

Murray is self-contradictory; he writes that our book ?synthesizes a considerable literature on infectious disease and U.S. economic history, particularly before 1900,? yet in the very next paragraph he claims that ?Much of the authors? case moves forward without reference to work of previous historians.?? This is insensible.? We do not know how to interpret his second comment that we are deficient in referencing; there are 27 pages in the ?References? containing nearly 500 entries, each cited in the text.? Murray does mention four works that we did not cite that he thought we should have.? Yet he chose to write a review that reads as if we cited none.? (If his criticism is that the book is not littered with footnotes, he is correct; we made a conscious choice to minimally footnote to make it more readable.)

Murray states: ?Readers familiar with the work of world historians such as William McNeill, Philip Curtin, or Alfred Crosby, or historians of medicine such as Kenneth Kiple, Todd Savitt, or Margaret Humphreys will find little new here.?? With the exception of Humphreys, the books mentioned certainly influenced us, but to claim that there is little in our book that is not contained in them is grossly inaccurate.? As noted, Murray says little about our first four chapters, but, to repeat, that is where we outline why we think that the Malthusian theory on population is incorrect, yet Malthusian intuition associating increased human numbers with poverty is correct.? Not one of Murray?s authors writes about this.? An easy refutation of Murray is in our chapter 4; we may be wrong in our analysis and modeling of the use (and profitability) of African slavery versus European servants in early America, still it is ours alone.? We trust that anyone reading Parasites, Pathogens, and Progress can see that Murray?s claim that it is mostly in McNeill, Curtin, Crosby, Kiple, Savitt, or Humphreys is bizarrely inaccurate.? If it were true, why would Alfred Crosby state on our back cover: ?Scientists, economists, historians, and a goodly number of the rest of us have long recognized diseases as a powerful influence on the course of human experience, but we have harvested less than we could have from that insight because our familiarity with the subject is so thin.? We can do a lot to cure that by reading this excellent study, Parasites, Pathogens, and Progress??

Murray also states that our emphasis on a changing biological environment is old hat, claiming that ?after McNeill?s Plagues and Peoples (1976) and Crosby?s Ecological Imperialism (1986), very few scholars believe in a static global disease environment.?? We admit our debts to these scholars, but if everybody knows this, then why do the texts not reflect it?? The three major textbooks in U.S. economic history (Atack and Passell, 1994; Hughes and Cain, 2011; Walton and Rockoff, 2010) do not cite McNeill or Crosby, or mention the Columbian Exchange.? It is true, however, that the two more recent texts do cite earlier articles of ours on the nexus between disease susceptibilities and slavery.

There are at least three especially egregious claims in Murray?s review.? First, Murray writes: ?The bulk of the book is given over to the importance of infectious disease, primarily malaria, in determining that the labor force in the South would be drawn from African slaves? (emphases added).? How did he ever come up with the idea that the bulk of our book is primarily about malaria?? In what we say about southern diseases, hookworm has more pages and more entries to it in the References than does malaria, so Murray?s claim judged solely against hookworm is incomprehensible.? Moreover, the text and the Index have more allusions to infectious agents than any non-computer can spell.? We explicitly write about ?hookworm, malaria, yellow fever? and other warm-weather diseases in chapter 5 (see pp. 80-81, 83, 89-91, 97, 105-110), albeit concentrating on hookworm and malaria.? In chapter 6, there is (1) a 4-page section on ?Yellow Fever and the Southern Urban Disease Environment? (pp. 122-25), (2) an 11-page section on ?Slave Plantations and the Southern Rural Disease Environment? (pp. 125-35) that includes a subsection titled ?Nutritional and Parasitic Diseases on Southern Plantations? (pp. 127-35), (3) a 17-page section titled ?Hookworm? (pp. 138-54), and (4) a 17-page section titled ?Malaria? (pp. 154-71).? One of the points of our book is that morbid diseases were major factors in determining settlement patterns in the New World.? Any reader can judge how much emphasis we devote to hookworm and other infectious diseases, and then determine if our primary focus is on malaria.? To claim that when we write about the American South our focus is ?primarily malaria? indicates that the reviewer was not reviewing what was written.

The second egregious claim Murray makes is when he pieces together quotes from two unrelated sentences to change the meaning of what we wrote.? On our discussion of Africans? relative susceptibilities to cold-weather diseases, he writes ??As a result,? they write (p. 100), ?there is (sic) an increase in the migration of European indentured servants? to the northern colonies.? To explain the absence of evidence for this claim, they note (p. 100) that ?reliable data for indentured servants bound for New England are not available.??? We did not say that.? The first sentence Murray quotes (?As a result, there is an increase in the migration of European indentured servants.?) is from a paragraph that begins on p. 99 in the book where the discussion is about the migration of Europeans to northern colonies.? The second quote (?reliable data for indentured servants bound for New England are not available?) is found two paragraphs later on p. 100 and is not related to the first quote.? It comes from a paragraph that begins with the following sentence: ?We can now illustrate the economic case for the relative absence of Africans in the northern colonies? (p. 100, emphases added).? Murray inserted his own clause (?To explain the absence of evidence for this claim?) after the first quote from our book, attaching it to the beginning of an unrelated clause in another sentence and completely changed the meaning of what we wrote.? The complete second sentence we wrote is: ?Because reliable data for indentured servants bound for New England are not available, we chose to utilize data about servants for the northern-most colony for which reliable data exist for the eighteenth century? (p. 100).? To repeat, the referred to data were utilized to ?illustrate the economic case for the relative absence of Africans in the northern colonies? (p. 100).

The third egregious claim of Murray is that he states ?the lack of such data [on New England servants], reliable or otherwise, was due to the tendency of indentured servants to avoid New England in the first place.?? Murray is wrong; he is writing as if he does not know about the migrations to America during the Colonial Period.? Because a large consistent dataset is not available, does not mean a market (or migrations) did not exist.? In chapter 5, we estimate the annual flows of indentured servants from data that are available on the stock of indentured servants in the three regions of colonial America.? The data on the number of indentured servants in New England (and in the other two regions) come from Edwin Perkins (1980) whom we regard as highly competent and a reliable source.? By making a few simplifying assumptions, we were able to estimate the flow of indentured servants into New England from its stock.? This is all detailed on page 102.? So what we have here is a reviewer taking what we would say was a careful explanation of how we derived annual flows from the stock of indentured servants, and then saying because explicit data on annual flows did not exist, the market did not exist.? If the market did not exist because of ?the tendency of indentured servants to avoid New England,? then, in the absence of spontaneous generation, where did the stock of indentured servants come from?

Murray entirely missed that chapter 5 is (1) about why Africans predominated in the southern colonies and northwest Europeans predominated in the northern colonies and (2) that our entire argument is about the relative nature of our hypothesis.? Relatively more Europeans (and indentured servants) went to New England than Africans; nothing in our hypothesis says anything about the absolute number of indentured servants going to New England compared to the total number going to the Middle colonies.? We provide evidence on the relative predominance of African slaves in the southern colonies and the relative predominance of Europeans (and indentured servants) in the northern colonies (pp. 100-102).

There are several other issues about our book that bedevil Murray.? He is concerned that we did not cite a source on the spread of disease in nineteenth-century America which, according to him, would have bolstered our case.? But the mentioned source has no explicit evidence on disease and contains biased data.? Murray criticizes our very brief discussion of the Antebellum Puzzle at the end of chapter 3 for its assertions and lack of evidence.? But he fails to note that the page and a half discussion was intended only as an example (and is titled as such) of the thinking contained in our model of long-run growth presented in chapter 3.? The evidence for the links between demographic and transportation developments and the spread of diseases is presented in chapter 7, and, additionally, in two appendices that present data on the links among density, urbanization, cities, population growth, and transportation (and other exchange facilitating) developments, and the spread of disease.? Murray believes that our discussion of differential disease (he incorrectly says malaria) susceptibility ?and its consequences for our history is widely accepted by historians.?? We are unaware of this wide acceptance, and we have no knowledge of any historians who blended together an analysis of the profitability of slavery with the differential effects of hookworm, malaria, and the other biological agents that are the major elements in chapters 5 and 6.? Murray also complains about our not documenting the use of quinine, yet everybody who is marginally conversant with malarial diseases in the nineteenth century knows about quinine.? Even Wikipedia recognizes the ubiquity of quinine; its entry on quinine states that it was commonly used prophylactically circa 1850 (its clinical usage predated 1850). What is commonly known should not be cited.? And, yes, we do write that ?it [quinine] was widely known and efficacious in combating malaria? (p. 161) without citation, still two pages later (p. 163) we cite Curtin (1989) as ascribing the reduction in malarial mortality to the increasing use of quinine after 1820.? A reduction in mortality should be enough to alert a perceptive reviewer to how widespread quinine was even in the absence of specific knowledge.

Murray?s reading of our book is very eccentric; it is akin to reading Walden as a survivalist guide.? We believe the review is orthogonal to objective reality; however, these are judgmental statements.? Readers can make up their own minds; after reading Parasites, Pathogens, and Progress, feel free to let us know if you think Murray?s depiction of its contents is reasonably adequate and complete.


Atack, Jeremy, and Peter Passell (1994) A New Economic View of American Economic History from Colonial Times to 1940, 2nd edition, New York: W. W. Norton & Company.

Curtin, Philip D. (1989) Death by Migration: Europe?s Encounter with the Tropical World in the Nineteenth Century, New York: Cambridge University Press.

Hughes, Jonathan, and Louis P. Cain (2011) American Economic History, Boston: Addison-Wesley.

McNeill, William Hardy (1976) Plagues and Peoples, New York: Anchor Books.

Perkins, Edwin J. (1980) The Economy of Colonial America, New York: Columbia University Press.

Walton, Gary M., and Hugh Rockoff (2010) History of the American Economy, 11th edition, Mason, OH: South-Western, Cengage Learning

Robert A. McGuire is a research professor of economics at the University of Akron; Philip R. P. Coelho is a professor of economics at Ball State University.

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