Razzell argues that the quality of smallpox recording in the Marine Society data set is so poor that ‘the impact of smallpox on average height cannot be settled by analysis of the Marine Society data set’. We believe that this grossly overstates the problems of the records, and is based on a careless reading of the original records on his part. Furthermore, insofar as his claim that some of the boys who are recorded as escaping smallpox had in fact suffered the disease, the direction of bias strengthens rather than weakens the statistical evidence that smallpox reduced height.

Leunig, Tim

Voth, Hans-Joachim

English

Research Papers in Economics

 
 
 
LSE Research Online 
 
Article (refereed) 
 
 
 
 
Tim Leunig and Hans-Joachim Voth  
 
Smallpox really did reduce height : a reply to 
Razzell 
 
 
 
Originally published in Economic history review, 54 (1). pp. 110-114 © 
2001 Blackwell Publishing. 
 
You may cite this version as:  
Leunig, Tim & Voth, Hans-Joachim (2001). Smallpox really did reduce 
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Contact LSE Research Online at: Library.Researchonline@lse.ac.ukSmallpox really did reduce height: a reply to Razzell 
 
Timothy Leunig 
 
Department of Economic History, London School of Economics, Houghton St, 
London, WC2A 2AE.  
 
Hans-Joachim Voth  
 
Department of Economics, Universitat Pompeu Fabra, Barcelona and King's College, 
Cambridge 
 
Peter Razzell believes that we have misunderstood the nature of his criticism and are 
correspondingly dismissive of it. Nothing could be further from the truth. We share 
every professional historian’s concern for the integrity of the data. Indeed in other 
work that we have done, we have 'left our computers' and have both proven keen 
archival historians.
1  
 
Razzell argues that the quality of smallpox recording in the Marine Society data set is 
so poor that ‘the impact of smallpox on average height cannot be settled by analysis 
of the Marine Society data set’.
2 We believe that this grossly overstates the problems 
of the records, and is based on a careless reading of the original records on his part. 
Furthermore, insofar as his claim that some of the boys who are recorded as escaping 
smallpox had in fact suffered the disease, the direction of bias strengthens rather than 
weakens the statistical evidence that smallpox reduced height.  
 
At the heart of the reliability issue is the method of recording whether a boy had 
suffered smallpox. The Marine Society Registrars recorded that a boy had had 
smallpox by placing a p in the column labelled ‘spox’, leaving it blank otherwise. 
  1Similarly they recorded a person as literate by placing an r in the reading column and 
a w in the writing column, leaving them blank otherwise. The computerised data set 
likewise contains a mark where the original records have one, and a blank otherwise. 
Interpreting a p in the spox column is thus straightforward: the registrar clearly 
believed the boy to have had smallpox. The adequacy of smallpox registration thus 
turns on our interpretation of a blank in the smallpox column. If the registrar was 
conscientious, a blank in the spox column would indicate that the registrar believed 
that the boy had not had smallpox. If the registrar was incompetent or negligent, a 
blank would indicate that he failed either to ask the question or to record the answer. 
In claiming ‘complete inadequacy of smallpox registration’ Razzell is arguing that the 
registrars frequently failed to fill in their registers properly.  
 
He bases this conclusion on a comparison of the columns for literacy and smallpox. 
He argues that if the columns for reading and writing as well as smallpox are blank, it 
is more likely that the returning officer was negligent. Although no one can doubt that 
some of the thousands of boys entering the society were illiterate as well as had 
escaped smallpox, it would indeed be cause for concern were there to be long series of 
boys for whom there were no marks in any of the three columns. Razzell then goes on 
to look at how frequently those boys recorded as escaping smallpox were also 
recorded as being illiterate. It is this literacy test that he claims ‘reveals the complete 
inadequacy of smallpox registration.’ But his investigation is seriously flawed. He 
claims, for example, that in the years 1777-1778 there are 151 boys listed as having 
escaped smallpox.
3 This is simply not correct: the original records show that there 
were 197 boys in those years who had not had smallpox.
4 More importantly Razzell 
claims that in the 71-year period in which the Marine Society collected data on 
smallpox there are only 29 boys recorded as being literate and escaping smallpox.
5 In 
fact the original records show that there are more than this number in the first dozen 
years alone, and more than three times this number in total.
6 Razzell claims to have 
‘provided the new economic history with an invaluable lesson – there is no substitute 
  2for the scrupulous study of original source material’; given his archival errors we 
suggest that this message needs to be learned by old as well as new economic 
historians.  
 
As new economic historians we make no claim that the data is perfect. No doubt the 
original records contains both honest error and pieces of poor recording. One of the 
most powerful features of statistics is that it does not demand perfect data to give 
meaningful results. In this case, in fact, to the extent that Razzell is right that some of 
the boys recorded as having escaped smallpox had in fact suffered the disease, it 
strengthens, not weakens, our results. This is seen most clearly through a numerical 
example.  
 
We found that those boys with a p in the smallpox column were statistically shorter 
than those boys who did not have a p in that column. That much is not in dispute. Let 
us imagine – for simplicity – that, correcting for age and other factors, we found that 
the height of the former group was 54 inches and that the height of the latter group 
was 55 inches. If the records are perfectly accurate it follows that smallpox reduced 
heights, and did so by one inch. Imagine now that Razzell’s criticisms are well 
founded, and that half of the boys without a p in the smallpox column had in fact 
suffered smallpox but that this was not recorded by hasty registrars. What then would 
we know? We would still know that the height of those with smallpox was 54 inches 
– again, that much is not in dispute. But we would also know that the average height 
of a group made up half of boys with smallpox and half of boys without smallpox was 
55 inches. Since we know that the half with smallpox averaged 54 inches in height, it 
follows that the half without smallpox must have been 56 inches tall to yield an 
average of 55 inches for the mixed group. In this case those who suffered smallpox 
were two inches – rather than one inch – shorter than those who had not suffered the 
disease. In short, if Razzell is right that some of the boys recorded as escaping the 
disease had in fact suffered it, not only does our conclusion that smallpox reduced 
  3height remain correct, but it means that the true effect of smallpox on height would be 
even larger than we originally argued.  
 
Let us turn now to the data itself. Razzell has stated that ‘genuine cases of “no 
smallpox” can possibly be recognised by their occurrence in individual entries with 
information on reading or writing’.
7 In effect, if a boy has a mark in the literacy 
column we can be more certain that his recording officer was conscientious, and, as 
such, more certain that his smallpox information is reliable. Although we think 
Razzell is pessimistic about the registrars’ diligence, we are happy to use the literate 
sub-sample of boys to test whether smallpox did indeed reduce height. 
 
In order to show not just that smallpox reduced height, but that following Razzell’s 
recommendations strengthens rather than weakens our results, we test for the effect of 
smallpox on both the whole sample and on that sub-group recorded as literate. We use 
data beginning with the first person to be recorded as suffering from smallpox and 
ending in 1841, the last year in which we see entries in the smallpox column. Since 
the minimum height standard changed over this period, we also include a dummy 
variable for each of the sub-periods.
8 These capture not only the changes in the 
Marine Society’s minimum height standards, but also more general changes in living 
standards over time.  
 
Regression about here. 
 
The results are clear and unambiguous. In both regressions smallpox is shown to 
reduce height. In both cases the co-efficient on smallpox is significant at the one per 
cent level. Those who are more optimistic about the quality of the recording process 
will favour using the whole sample. More sceptical researchers will prefer to look 
only at those recorded as being literate. In either case they will conclude that smallpox 
did indeed reduce heights.  
  4 
As basic logic would lead us to expect, following Razzell’s advice to look only at a 
more restrictive set of data (about which we can be more confident) strengthens rather 
than weakens our conclusion. Our estimate of the height reducing effect of smallpox 
rises from a quarter of an inch to three quarters of an inch. The reasoning is exactly as 
for the earlier numerical example. It is worth noting that the regression performs well 
more generally. Those who are older are taller, as are those admitted when there was a 
higher minimum height standard. With the exception of literacy, every variable is 
significant at the one per cent level. 
 
What then should we conclude? First, we can say, more clearly than before, that 
smallpox reduced heights. Second, the difference between the estimates of the effect 
of smallpox on height in the two regressions do indeed indicate that there were 
periods in which the registrars were less conscientious than historians would like them 
to have been. Third, as we have shown, the effect of such errors does not invalidate 
the work of new economic historians using the data set; instead it strengthens their 
results.  
 
Rigorous archival and statistical examination confirms that one of the most infectious 
and deadly diseases not only left many survivors scarred for life, but also stunted their 
growth. This should not surprise us. We know from contemporary medical research 
that measles has substantial effects on the nutritional status of children in the third 
world.
9 Since smallpox was, by all accounts, a far more virulent and life-threatening 
disease than measles, to conclude that smallpox did not reduce heights would pose a 
medical puzzle. 
 
Such a result would also pose a problem for anthropometric history. It has as its 
cornerstone the claim that attained height reflects an individual’s cumulative 
nutritional status during childhood – including the effect of disease. Were we to find 
  5that the ‘most terrible of all the ministers of death’ did not affect the attained heights 
of those who survived, then we would be forced to question the very basis of 
anthropometric history.
10 We have been able to go further than showing simply that 
smallpox reduced heights, and have been able to estimate the height loss at a little 
under 1 inch. As we suggested in our original article, we see this finding as furthering 
anthropometric history by beginning to answer Crafts’ objection that anthropometric 
historians need to ‘pin down links between the various aspects of the quality of life 
and height.’
11 The movement from endemic smallpox to no smallpox would have 
raised average attained heights by a little under one inch. Once we know how attained 
heights alter with changes in working hours, the age at which children start work, 
nutritional intake, over-crowding, and so on, we will be better able to interpret the 
changing heights of individual populations over time, and the height differences 
between populations. Then we will be better placed to do what all economic and 
social historians, new and old, seek to do: to understand and explain the standard of 
living in different societies, at different times. 
 
 
  6Table 1. The determinants of height 
 
 
 1  2 
Smallpox -0.25  -0.75 
 (-3.0)  (-3.2) 
Age years  1.68  1.67 
 (162.0)  (125.9) 
Read 0.07   
 (1.7)   
Write 0.43  0.44 
 (11.3)  (11.3) 
1786-91 (54 inches)  0.61  0.67 
 (12.2)  (10.3) 
1792-97 (52 inches)  0.22  0.26 
 (5.0)  (4.4) 
1798-1808 (54 or 52 inches)  -0.55  -0.48 
 (-12.9)  (-8.7) 
1809-11 (50 or 51 inches)  -1.40  -1.30 
 (-24.5)  (-17.3) 
1812-13 (51 inches)  -1.29  -1.26 
 (-19.4)  (-15.4) 
1814-17 (54 inches)  0.43  0.44 
 (4.9)  (4.1) 
1818-20 (55 inches)  1.87  1.90 
 (14.5)  (12.8) 
1821-23 (56 inches)  2.73  2.74 
 (24.6)  (22.6) 
1824-41 (57 inches)  3.35  3.29 
 (54.4)  (47.9) 
Intercept 30.40  31.10 
 (180.9)  (102.5) 
Adj R
2 0.65  0.65 
S.E. 2.18  2.20 
F 3371.5  2348.5 
N 23971  15173 
of which, with smallpox  23206  15085 
 without  smallpox  765  88 
 
 
Notes: 
Regression one includes all boys, regression two is limited to those recorded as being 
literate. 
t-statistics in parentheses 
The estimation technique is OLS, estimated using Stata 6 
The omitted sub-period is 1770-1785 (minimum height standard, 51”) 
 
 
 
  7References 
 
Crafts, N.F.R., 'Cliometrics, 1971-1986: a survey', J. App Econometrics, 2 (1987), pp. 
171-92 
 
Floud, R. C., Wachter, K. W., and Gregory, A. Height, health and history: nutritional 
status in the United Kingdom, 1750-1980 (Cambridge, 1990) 
Krishnamurthy, K. and Anantharaman, V., 'Measles – a dangerous disease: a study of 
1000 cases in Madurai', Indian Pediatrics, 11 (1974) pp. 267-71 
Leunig, T. and Voth H.-J., ‘Smallpox did reduce height: a reply to our critics’, Econ. 
Hist. Rev., LI (1998), pp. 372-81  
Macauley, T. B., The History of England from the accession of James the Second, II 
(1889) 
Reddy, V., 'Interaction between nutrition and measles', Indian J. of Pediatrics, 54 
(1987), pp. 53-7 
Razzell, P., ‘Did smallpox reduce height?’, Econ. Hist. Rev., LI (1998), pp. 351-9 
Razzell, P., ‘Did smallpox reduce height? A brief comment’, Econ. Hist. Rev., (This 
issue). 
Voth, H.-J. and Leunig, T., ‘Did smallpox reduce height? 'Stature and the standard of 
living in London, 1770-1873’, Econ. Hist. Rev., XLIX (1996), pp. 541-560. 
Voth, H.-J., ‘Time-use in eighteenth century London’, J. Econ. Hist., 58 (1998), pp. 
29-58. 
  8 
                                                 
1 Among other work, Leunig has just collected 12500 pay roll records from the archives of a New 
England cotton mill, and Voth has assembled and analysed some 8,000 court records from Old Bailey 
Sessions Papers as well as hundreds of Northern Assize depositions. Voth, ‘Time Use’. 
2 Razzell, ‘Brief comment’, last para. 
3 Razzell, ‘Brief comment’, p. 2, para 2. 
4 We have supplied the Editor with the Marine Society reference numbers for each of the individuals, 
and we are happy to supply the list to interested readers. 
5 Razzell, ‘Did smallpox reduce height?’, p. 357 
6 Again, we have supplied the Editor with the Marine Society reference numbers, and we are happy to 
supply the list to any interested reader. 
7 Razzell, 'Did Smallpox?' 
8 The sub-periods are listed in Floud et al. Height p. 164 
9 Krishnamurthy and Ananthraraman, ‘Measles’, Reddy ‘Interaction’ 
10 Macauley, History of England, II, p. 498 
11 Crafts, ‘Cliometrics’, p. 189 
  9

Smallpox really did reduce height : a reply to Razzell.

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