Public Use Microdata Samples of the 1860 & 1870
U.S. Censuses of Population1
by J. David Hacker, Steven Ruggles,
Andrea R. Foroughi, and Walter L. Sargent
In 1997 the Historical Census Projects at the University of Minnesota began construction of public use microdata samples of the 1860 and 1870 U.S. Censuses of Population.2 The samples are machine-readable transcriptions of the original census manuscripts, suitable for computerized data analysis. Among their many applications for historical research, the two census samples will allow social scientists the opportunity to examine such important topics as black and white family structure, the distribution of wealth, the growth of female employment, and the demographic consequences of the American Civil War.
The new samples bridge the gap between the existing 1850 and 1880 samples, increasing the latter's usefulness for the study of long-term change and eliminating the need for researchers to interpolate results over this critical thirty-year period. The purpose of this article is to suggest some possible uses of the 1860 and 1870 samples, briefly examine concerns about a suspected undercount in the 1870 census and provide background information on the construction of the samples and their availability.
Using Census Microdata in Historical Research
Until the recent release of the 1850 and 1880 public use microdata samples (Ruggles and Menard 1994; Ruggles and Menard 1995), nineteenth-century historians were forced either to construct their own samples from copies of the original manuscript returns or to rely on official census returns published by the U.S. Census Office (as the Census Bureau was known before 1902). In 1790, official census reports included little more than population totals tabulated by sex, age group, race and state. After 1830, however, published tabulations become more detailed and thus more valuable to social scientists. By 1870 the Census Office report on the census of population included over 40 cross-tabulations, making it possible for researchers to conduct a variety of population analyses (Magnuson 1995).
Despite the increasing detail provided by the Census Office, published census data from the nineteenth century fall far short of their potential usefulness. Different census years employed differing tabulation designs, making it difficult or impossible to evaluate change over time. For example, the 1870 census publications listed the number of individuals working in various occupations by age, sex, race, nativity and state, but the 1860 census only cross-tabulated occupation by state. Budgetary constraints also prevented the Census Office from conducting detailed analyses of some questions. The Census Office carried out no analyses of some items in the 1860 and 1870 censuses, such as the value of each individual's real and personal estates, whether married in the year, citizenship, or citizens denied the right to vote. Using the published information from 1860 or 1870, it is also impossible to investigate such important topics as the living arrangements of the elderly, female-headed households, single parenthood or nuptiality.
Census samples drawn from the original enumerator's manuscripts eliminate many of the problems associated with published census data. Sampled dwellings are entered from microfilm copies of the original manuscript returns, and the answers are coded to simplify quantitative analysis. Public use microdata samples maintain a unique record for each dwelling and person in the sample-thus their designation as microdata-allowing researchers to make tabulations tailored to their specific research questions. Questions unexplored by the Census Office in its published tabulations can be analyzed for the first time. New variables can be constructed based on family or dwelling characteristics compatible with later years.3 Perhaps most important, researchers can apply modern multivariate methods designed for the analysis of individual-level data.
With the creation of the 1860 and 1870 samples, researchers have a continuous series of microdata for most census years between 1850 and 1990. Only samples from the 1890 and 1930 censuses are missing: the 1890 census was destroyed by fire and the 1930 census is subject to confidentiality statutes until 2003.
Research Opportunities with the 1860 and 1870 Microdata Samples
We have described elsewhere some potential applications of high-precision census microdata for historical research (Ruggles 1991a, 1991b, 1993; Ruggles and Menard 1990, 1995). It is worth briefly noting, however, four particular strengths of the 1860 and 1870 samples.
First, since slaves were never enumerated in detail, 1870 was the first census year to provide detailed information about the black population. The 1870 sample will therefore serve as the baseline for demographic and economic studies of American blacks. For example, recent studies have shown that the black pattern of single-parent residence is considerably older than was previously thought (Ruggles 1994a; Morgan, McDaniel, Miller, and Preston 1993); the 1870 sample will allow researchers to push the analysis back to the period of Reconstruction and to investigate the relationship of single parenthood to local economic and agricultural systems. More broadly, data from the 1870 sample will enable social scientists to reassess a wide range of key characteristics of the newly freed population, including geographic mobility, fertility, nuptiality, occupational structure, wealth distribution, property ownership, literacy, school attendance and voting status. The 1860 and 1870 samples are especially useful for studying the black population since they include an oversample of dwellings with one or more black individuals which will ensure sufficient cases for detailed analysis of the former slave population.
The second strength of the new samples is their potential for studying the impact of the Civil War. The 1860 and 1870 censuses bracket the period of the war, and are therefore likely to prove invaluable for historians of the conflict. The Civil War has been described as the first "total war," affecting society at all levels in both the North and South (McPherson 1996). Historical demographers are only beginning to investigate its massive demographic impact (Vinovskis 1990; Hacker forthcoming). The 1860 and 1870 microdata samples will provide the raw material for individual-level analysis of the wartime fertility deficit, disruptions in the incidence and timing of marriage, and interstate migration that resulted from the war. Because the samples are nationally representative, they will allow scholars to make regional comparisons of the war's demographic impact for the first time.
Unique census questions on wealth in 1860 and 1870 constitute a third peculiar attribute of the new samples. The 1860 and 1870 census files will provide the only representative national microdata with full information on personal wealth before the late-twentieth century. Several recent studies suggest that inequality in the distribution of wealth in the United States grew more rapidly during the middle nineteenth century than at any other time in American history. The scarcity of individual-level data, however, has led to considerable uncertainty concerning the extent of inequality and the shape of the distribution (Lindert and Williamson 1980; Shammas 1993). The inclusion of questions on the value of real and personal property owned by each individual will make the 1860 and 1870 samples a unique resource for the study of wealth distribution. Although Francis Walker, superintendent of the 1870 census, expressed concern about the reliability of these inquiries, recent research has verified a close correspondence between local tax assessments and the 1870 census returns (Blocker 1994). These new data will support fruitful research based on the relationships between the characteristics of families and their level of wealth.4
The final strength of the new samples is their potential for studying female labor. The 1860 census was the first to record female occupations but the results were not even tabulated separately for women in the published reports. The late-nineteenth century witnessed a dramatic increase in women's participation in the wage-earning workforce, although the number of women employed in the relatively well-paid dress-making and millinery trades declined over time (Sobek 1997, Gamber 1997). The 1860 and 1870 microdata samples will therefore serve as a baseline for understanding the implications of changing female employment. Recent research has also suggested that published data on female employment in the 1880 census were biased downwards, further increasing the value of the 1870 sample (Carter and Sutch 1996).
These topics are intended only as illustrative examples of some of the more promising areas for new research that can be pursued with the 1860 and 1870 microdata. The new samples will become an essential resource for the study of the social and economic transformations of the Civil War era, including urbanization, industrialization, westward expansion, and immigration. They will allow investigation of changes in industrial and occupational structure, the family economy, household composition, internal migration, life-course transitions, fertility, nuptiality, school attendance and literacy. For each of these topics, the samples will provide information on the interrelationships among personal and household characteristics that cannot be obtained from any other source. Moreover, the 1860 and 1870 census files will be the earliest national samples to include key inquiries on value of personal estate, citizenship, voting status, parental foreign birth, month of birth, month of marriage, detailed literacy and occupational status of women. Table 1 shows a list of the variables that will be included in the 1860 and 1870 microdata samples, together with their availability in existing samples for the nineteenth century.
The 1870 Undercount
The 1870 census was carried out under the supervision of Francis Walker, the first Superintendent of the U.S. Census Office to bring a modern, statistical approach to the census (Anderson 1988). Walker took steps to improve the quality of the census, eliminating the practice of "farming out" subdivisions and "taking the census" at election and courts days-- practices he believed to have been prevalent in the South in previous censuses. Although Walker made clear his desire to reform further the laws governing the Census Office-and especially to reduce the length of the enumeration period-he expressed confidence about the high quality of the 1870 census.
It is believed that the enumeration of the people at the present census has been as carefully and honestly performed in every part of the country, as at any preceding period. In no section has the percentage of loss, taking city and country together, been considerable. The field, on the whole, has been thoroughly gleaned, and, in the great majority of subdivisions, far more pains have been taken, under the stimulus of public criticism, than the Government paid for, or had reason to expect." (U.S. Census Office 1872: xix).
Walker's defense of the 1870 census took place in the context of considerable public criticism of the enumeration. The population count was lower than expected, and widespread disappointment in the national growth rate aroused suspicions of large-scale census underenumeration. Complaints of excessive undercounts in New York and Philadelphia were especially bitter and resulted in the unusual step of the President ordering a recount. Yet, Philadelphians believed that as much as a third of its population had not been enumerated; the recount, taken in the winter when the population was more likely to be indoors and with rigorous efforts on the part of city officials to ensure full enumeration, resulted in an increase of only 2.5 percent. New York's recount found only 2 percent more people (U.S. Census Office 1872: xx-xxi).
Disappointment in the nation's population growth two decades later would again result in charges of underenumeration in the 1870 census. In the 1890 census report on population, the Census Office found the national growth rate between 1880 and 1890 was far lower than the growth rate from 1870 to 1880. To explain this "disappointing" decline, they argued that the 1870 population was underenumerated. Only after inflating the 1870 population of 13 southern states by over 1.2 million (3.3 percent of the nation's population) were investigators satisfied with decennial growth rates (U.S. Census Office 1897: xi-xii). Although no modern investigation has been conducted to verify their adjustments, concern still lingers among social scientists about the possibility of excessive undercounts in the 1870 census.
A full examination of the potential 1870 undercount will not be possible before the 1860 and 1870 samples are completed. Our preliminary investigation of the 1870 population figures, however, indicates that the undercount estimate given in the 1890 census report was greatly exaggerated. To arrive at the estimated 1.2 million-undercount, the 1890 investigators assumed that the South experienced steady population growth between 1860 and 1880. Recent studies, however, have suggested that the Civil War was a demographic catastrophe for the South. Sixty-one percent of southern white men fought in the war and approximately one in four (258,000) died. The high mortality of southern white men and their lengthy service in the Confederate Army was undoubtedly a significant factor in the concomitant decline in fertility among females age 20 to 49. Our analysis of aggregate census data indicates a 26 percent drop in fertility among southern white women during the war years, representing a deficit of over three hundred thousand births. No comparable wartime fertility deficit is evident in the North. By 1880, fertility rates in the South had rebounded, to rise above the pre-war level. Researchers also believe that net in-migration to the South followed a similar pattern, falling dramatically in the decade 1860-70 and recovering in the decade 1870-80 (Vinovskis 1990:12; Goldin 1980:935-57).
Taken collectively, this initial investigation of mortality, fertility, and migration suggests that the pattern of white population growth in the South is much more accurately described by the originally reported census figures than by the 1890 revision. Black population trends are more difficult to estimate. Analysis is hampered because the 1870 census was the first year most blacks were tabulated in detail. Given the disruptions caused by the war and the social chaos following emancipation, Francis Walker maintained that southern blacks experienced exceptionally high mortality and low fertility during the 1860s. He concluded that "it is only to be wondered that the colored people of the South have held their own in the ten years since 1860" (U.S. Census Office 1872: xvii). Ransom and Sutch have applied life table techniques to the published census data and arrived at a black undercount of about 6.6 percent (Ransom and Sutch 1975). Although a definitive analysis of Southern undercounts awaits completion of the 1860 and 1870 samples, we are confident that underenumeration of southern whites and blacks in 1870 was far lower than 1890 investigators estimated. Certainly, the 1870 undercount compares favorably with nonresponse rates routinely encountered in modern social survey data, and will not pose a significant problem for most analyses.
Figure 1 shows the enumeration form used by the 1870 census of population. The 1860 census form is virtually identical, except that it lacks the fields on parental foreign birth, month of birth for infants, and citizenship. The manuscript censuses for 1860 and 1870 consist of two million of these forms, with a maximum of 40 persons per form. These records are contained on 3,186 reels of microfilm. The enumeration covers the population of all states and territories that existed at the time the census was taken - a geographic area roughly equivalent to the lower 48 states today. In both census years, however, the enumeration excludes "Indians not taxed," meaning Indians residing on reservations, in unorganized territories, and elsewhere beyond the reach of European settlement. In addition, in 1860 the slave population was enumerated on a separate, highly limited schedule which we plan to sample separately (see below). The microfilm reels are complete in the sense that they include all the original enumeration manuscripts.
The 1860 and 1870 samples are designed to allow high precision estimates of characteristics of the population as a whole or for population subgroups. This is a different approach from existing samples drawn from the 1860 and 1870 census manuscripts - most notably Bateman and Foust (1989) - which are designed to maximize contextual information but offer lower precision and focus on particular localities and regions.
We maximize precision through two key sample design features. First, we sample systematically from the microfilm reels at intervals of approximately every sixth page or 500 census lines. Once we have located a census page, we randomly identify a "window" of five lines on the page, and include in the sample any dwelling beginning on one of those lines. This procedure ensures equal probabilities of inclusion, regardless of dwelling size. It yields, in effect, a geographically stratified 1 in 100 sample of dwellings which offers substantially higher precision than would a true random sample of dwellings.
Our second procedure to maximize precision is a group quarters concept. Very large units undermine sample precision, because of the effects of clustering. For example, the 1870 sample when complete will contain perhaps 1200 persons in institutions. If we sampled large institutions as intact units, the 1870 sample would include only a handful of such institutions, and the odds are low that they would be representative. Therefore, when we encounter dwellings with more than 30 members, we sample them as if they were individuals residing in one-person dwellings. If our window of five sample points falls within a large unit, we take all five individuals regardless of whether or not the unit begins within the window. Thus, we end up with a representative 1 in 100 sample of individuals residing in large units.5
Many of the key analytic questions in 1860 and 1870 concern the black population. Since 1870 was the first year to include detailed information on the entire black population, it must serve as the baseline for many studies. Since the size of the black population was fairly modest, we decided to oversample it. Thus, we gathered data on 1-in-50 households containing blacks, and 1-in-100 households not containing blacks. On half the pages, we took all valid cases whether or not the unit included a black; on the other half of pages-the oversample pages-we only included the unit if a black person was present.
Oversamples of blacks and Hispanics were also carried out for the 1910 microdata sample (see Gutman and Ewbank elsewhere in this issue). The 1910 oversamples were created after the rest of the 1910 sample was complete, which meant that each reel had to be reexamined. By doing the 1860 and 1870 oversamples at the same time as the flat samples, we cut costs considerably. Moreover, the 1860 and 1870 census schedules have a tally of the number of blacks and whites on the bottom of each census schedule. In regions with few blacks, such as the rural North, a quick glance at this tally was all that was needed to know that no blacks appeared on the census page. Our analysis of the first half of the database shows that the oversample of blacks has precisely the same density as the flat sample of blacks, which suggests that the procedure worked highly reliably.
We have released two versions of the 1860 and 1870 samples: one flat version without the extra cases of dwellings with blacks, and one including the oversample. Weighting variables included in the samples allow researchers to obtain representative statistics using all available cases. The final samples, scheduled for completion and public release in 2002, will yield information on approximately 729,000 individuals living in 150,000 dwellings (see Table 2).
We also plan two 1-in-100 samples of the slave schedules of the 1860 census. Although the precise design is not finalized, we plan a 1-in-100 sample of slave schedules linked to owner schedules. Since linkage failures are likely to introduce some selection bias, we plan a second 1-in-100 unlinked sample of slave schedules. Although census enumerators collected only limited information about the characteristics of slaves, the information they did gather - including exact age and sex - is useful for evaluating underenumeration of blacks in 1870 and the demographic impact of the Civil War on the black population.
Both the 1860 and 1870 samples were designed from the start to be compatible with the Integrated Public Use Microdata Series (IPUMS), a series of twenty-five high-precision samples of the American population drawn from thirteen federal censuses between 1850 and 1990. The steps required to construct datasets for 1860 and 1870-sampling the original manuscript returns, data entry, data checking and verification, numeric coding, new variable construction, and allocation of missing and inconsistent data-have been discussed in detail elsewhere (Gardner 1995a, Block and Starr 1995, Kallgren and Ryden 1995, Sobek and Dillon 1995, Ruggles 1995b, Goeken and Mulcahy 1995). Documentation of variables in the 1860 and 1870 samples including frequency distributions-will be incorporated into the IPUMS User's Guide (see Hall and Fitch elsewhere in this issue). The procedural histories of the construction of these samples will be available with other IPUMS documentation. A preliminary 1-in-200 version of the 1860 and 1870 samples was released in 1998. Release of the final samples and documentation is scheduled for 2002. All files contained in the IPUMS are available through the World Wide Web at http://www.ipums.umn.edu. Users accessing data from the IPUMS website have the option of downloading complete sample files or using the extract system to select variables and perform case selections prior to downloading the data.
- This article appeared in Historical Methods, Volume 32, Number 3, Pages 125-133, Summer 1999. Reprinted with Permission of the Helen Dwight Reid Educational Foundation. Published by Heldref Publications, 1319 18th St. N.W. Washington, D.C. 20036-1802. Copyright 1999.
- The 1860 and 1870 sample construction projects were funded by the National Institute of Child Health and Development, grant HD34572.
- For example, we have created a variable on family relationship compatible with later census years. The 1860 and 1870 censuses did not explicitly ask about family relationships, but in the great majority of cases there is sufficient information to reliably infer them. The 1860 and 1870 census instructions to marshals specified that within each household, "the names are to be written beginning with the father and mother; or, if either, or both, be dead, begin with some other ostensible head of the family; to be followed, as far as practicable, with the name of the oldest child residing at home, then the next oldest, and so on to the youngest, then the other inmates, lodgers and boarders, laborers, domestics, and servants" (Wright and Hunt 1900). Examination of the 1860 and 1870 census manuscripts suggests that this sequence was almost always followed correctly. In 1880, when family relationships were given explicitly, over 98 percent of households listed members in the prescribed sequence. In addition to this sequential information, the 1860 and 1870 censuses provides other valuable clues to family relationship: surname, age, sex, occupation, and birthplace. See Ruggles and Sobek (1995) for a full description of our imputation procedures. Overall, the method accurately identifies household relationship in later census years in about 97 percent of cases.
- For examples using smaller datasets see Soltow 1975; Campbell and Lowe 1977, Kearl, Pope, and Wimmer 1980; Yang 1984; Atack and Bateman 1987; Galenson and Pope 1989; Steckel 1990.
- The sample design is actually more complicated than this, since we have special procedures for multi-household dwellings and for family groups residing in group quarters; see Ruggles 1995b.
Anderson, M.J. 1988. The American census: A social history. New Haven: Yale University Press.
Atack, J. and F. Bateman. 1987. To their own soil: Agriculture in the antebellum North. Ames, Iowa: Iowa State University Press.
Bateman, F. and J. D. Foust. 1989. Agricultural and demographic records of 21,118 rural households selected from the 1860 manuscript census [computer file]. Bloomington, IN: F. Bateman and J. D. Foust, Indiana University, producers, 1987. Ann Arbor, MI: Inter-University Consortium for Political and Social Research, distributor.
Block, W.C. and D.L. Starr. 1995. Data entry and verification in the 1850, 1880 and 1920 public use microdata samples." Historical Methods 28: 63-65.
Blocker, J.S., Jr. 1994. Assessing sources for analyzing wealth and income: The U.S. federal manuscript census, federal income tax assessment lists and local tax assessment lists. Paper presented at the annual meeting of the Social Science History Association, Atlanta, Georgia (November, 1994).
Campbell, R.B. and R.G. Lowe. 1977. Wealth and power in antebellum Texas. College Station, Texas: Texas A&M University Press.
Carter, S.B. and R. Sutch. 1996. Fixing the facts, editing of the 1880 United States census of occupations: With implications for long-term labor-force trends and the sociology of official statistics. Historical Methods 29: 5-24.
Galenson, D.W. and C.L. Pope. 1989. Economic and geographic mobility on the farming frontier: Evidence from Appanoose County, Iowa, 1850-1870. Journal of Economic History 49: 635-655.
Gamber, W. 1997. The female economy: The millinery and dressmaking trades, 1860-1930. Urbana: University of Illinois Press.
Gardner, T. 1995a. Software development for the public use microdata samples. Historical Methods 28: 59-62.
Goeken, R. and M. Mulcahy. 1995. Geographical variables in the public use microdata samples. Historical Methods 28: 74-76.
Goldin, C.D. 1980. War. In Encyclopedia of American Economic History, 3 vols., edited by Glenn Porter, 3:935-957. New York: Scribner.
Graham, S.N. 1980. 1900 Public use microdata sample user's handbook. Seattle: Center for Demography and Ecology, University of Washington.
Hacker, J.D. 1999. The human cost of war: Population and family structure in the era of the American Civil War. Minneapolis: Ph.D. Dissertation, University of Minnesota.
Kallgren, D.C. and D.B, Ryden. 1995. Data consistency checking in the 1850, 1880 and 1920 public use microdata sample. Historical Methods 28: 66-69.
Kearl, J.R., L.P. Clayne, and L.T. Wimmer. 1980. Household wealth in Utah: 1850-1870. Journal of Economic History 40: 477-496.
Lindert, P.H. and J.G. Williamson. 1980. American inequality: A macroeconomic history. New York: Academic Press.
Magnuson, D. L. 1995. The making of a modern census: The United States census of population, 1790-1940. Minneapolis: Ph.D. Dissertation, University of Minnesota.
McPherson, J.M. 1996. From limited to total war, 1861-1865. In Drawn with the sword: Reflections on the American civil war. New York: Oxford Press. 66-86.
Morgan, S.P., A. McDaniel, A.T. Miller, and S.H. Preston. 1993. Racial differences in household structure at the turn of the century. American Journal of Sociology 98: 798-828.
Ransom, R.L. and R. Sutch. 1975. The impact of the Civil War and of emancipation on southern agriculture. Explorations in Economic History 12: 1-28.
Ruggles, S. 1991a. Comparability of the public use files of the U.S. census of population, 1880-1980. Social Science History 15: 123-158.
_____. 1991b. Integration of the public use files of the U.S. census of population, 1880-1980. American Statistical Association Proceedings of the Social Statistics Section, (American Statistical Association) 365-370.
_____. 1993. Historical demography from the census: applications of the American census microdata files. In Old and New Methods in Historical Demography, edited by in R. Schofield and D. Reher, 383-393. Oxford: Oxford University Press.
_____. 1994a. The origins of African-American family structure. American Sociological Review 59: 136-151.
_____. 1995b. Sample designs and sampling errors in the public use microdata samples. Historical Methods 28: 40-46.
Ruggles, S. and R.R. Menard. 1990. A public use microdata sample of the 1880 census of population. Historical Methods 23: 104-115.
_____. 1994. Public use microdata sample of the 1880 United States census of population: User's guide and technical documentation. (Inter-University Consortium for Political and Social Research)
_____. 1995. The Minnesota historical census projects. Historical Methods 28: 6-10.
Shammas, C. 1993. A new look at long term trends in wealth inequality in the United States. The American Historical Review, 98: 412-431.
Sobek , M. 1997. A century of work: Gender, labor force participation, and occupational attainment in the United States, 1890-1990. Minneapolis: PhD. Dissertation, University of Minnesota.
Sobek, M. and L. Dillon. 1995. Classifying occupations in the public use microdata samples. Historical Methods 28: 70-73.
Soltow, L. 1975. Men and wealth in the United States, 1850-1870. New Haven: Yale University Press.
Steckel, R.H. 1990. Poverty and prosperity: A longitudinal study of wealth accumulation, 1850-1860. The Review of Economics and Statistics 72: 275-285.
Strong, M.A., et al. 1989. User's guide to the public use sample 1910 United States census of population. Philadelphia: Population Studies Center, University of Pennsylvania.
U.S. Bureau of the Census. 1972. Public use microdata samples of basic records from the 1970 census: Description and technical documentation. Washington: GPO.
_____. 1973. Technical documentation for the 1960 public use microdata sample. Washington: GPO.
_____. 1982. Public use microdata samples of basic records from the 1980 census: Description and technical documentation. Washington: GPO.
_____. 1984a. Census of population, 1940: Public use microdata sample technical documentation. Washington: GPO.
_____. 1984b. Census of population, 1950: Public use microdata sample technical documentation. Washington: GPO.
_____. 1992. Census of population and housing, 1990: Public use microdata sample documentation. Washington: GPO.
U.S. Census Office. 1872. Ninth census-volume I. The statistics of the population of the United States. Washington: GPO.
_____. 1897. Report of the population of the United States at the eleventh census: 1890, vol. 1. Washington: GPO.
Vinovskis, M.A. 1990. Have social historians lost the civil war?: Some preliminary demographic speculations. In Towards a Social History of the Civil War: Exploratory Essays, edited by M.A. Vinovskis, 1-30. Cambridge, England: Cambridge University Press.
Wright, C., and W. Hunt. 1900. The history and growth of the United States Census. Washington: GPO.
Yang, D. 1984. Notes on the wealth distribution of farm households in the United States, 1860: A new look at two manuscript census samples. Explorations in Economic History 21: 88-102.