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Explore how IPUMS created this variable
Most IPUMS data transformations are performed using variable harmonization tables that specify how each value in the source data is recoded. Some variables also require programming logic in addition to the harmonization table. The harmonization documents for this variable are:
- Harmonization table
- No supplemental programming
- Instructions for interpreting harmonization documents
OCCHISCO is a uniformly coded classification of occupations that is consistent across all countries. It is the most complicated variable to code consistently in the pre-1950 samples, and the present documentation does not fully cover the issues addressed. We will be progressively adding to the level of detail available on this variable. For example, we will occasionally provide examples of common responses below each code so that users will be able to see what responses were coded where. Users with queries about the coding of specific occupations should contact the IPUMS staff in the first instance. Users interested in variation in occupational responses below the level of detail provided in the codes (e.g., distinguishing "caretakers" from "janitors") should look at the OCCSTRNG variable.
The codes for OCC were adapted from the Historical International Standard Classification of Occupations (HISCO) coding scheme. More information on HISCO is available in M.H.D. van Leeuwen, I. Maas and A. Miles. (2002) HISCO: Historical International Standard Classification of Occupations. Leuven: Leuven University Press. HISCO in turn is based on the International Standard Classification of Occupations from 1968, commonly known as ISCO-68. Information on HISCO can also be located at the HISCO database of occupational titles, and the International Institute of Social History.
More information on the adaptations IPUMS made to HISCO can be found in the article "Occupational Classification in the North Atlantic Population Project" (2003), Historical Methods, Vol. 36, No. 2 (Part 2), pp.89-96.
Structure of the classification scheme
The classification scheme is hierarchical, in the sense that each digit in the 5 digit codes introduces a new level of detail. Codes sharing the same first 1, 2 or 3 digits are considered to be increasingly similar. For example, all people working in agriculture have the first digit 6. The first digit of a code indicates the "Major group" a person's occupation is in.
The second digit indicates a "Minor group" distinction. Continuing the previous example, people who have the first two digits "61" are farmers - who may specify what they are cultivating or tending - and farm managers. Thus, as well as sharing the characteristic of working in agriculture (6) they also share the characteristic of being owners or managers (61).
The first 3 digits denote the "Unit group" of an occupation. At the third digit level, we introduce more detail. For example, the unit group "612" indicates "Specialized farmers". Within this unit group, 4th and 5th digit distinctions known as "titles" or "headings" are made. For example, "61220" indicates "Field crop farmers," and "61230" indicates "Orchardists and fruit farmers."
In general, if the last two digits of a code are "00" the heading is reserved for general titles. For example, in unit group "721" for "Metal smelter and furnace workers", the heading "72100" is reserved for responses such as "Metal smelter" and "Furnace men."
If the last two digits of a code are "10" the heading is reserved for "not further specified" titles (often abbreviated "n.f.s." or "nfs" in syntax files), and codes ending in "20", "30" and higher multiples of 10 are reserved for responses with more detail on some aspect of the occupation. For example, "58210" is the code for "Policemen and detectives, employer unknown," whereas "58220" and "58230" are the codes for "Policemen and detectives, public service," and "Policemen and detectives, private service" respectively.
Headings ending in digits other than "0" (e.g., 2, 3, 4, 9) are generally reserved for frequent responses specific to a particular country that probably belong with responses sharing the same first four digits of the heading. For example, "61115" ("Husbandman or cottar") in Norway and Sweden and "61117" ("Female farmer") in Canada could be classified with "Other general farmers" ("61110"), but occurred frequently enough that we felt they should be given a separate code for easier identification.
If the last two digits of a code are "90", the heading is reserved for "not elsewhere classified" responses. For example, "58290" is the code for "Other law enforcement officers".
The difference between "n.f.s." and "n.e.c." responses is that "n.f.s." responses are quite general, and may not offer much detail on the tasks and duties of the job. Conversely, "n.e.c." responses are typically quite detailed in the information provided, but there are not enough similar responses to justify a separate heading.
Alterations to HISCO
Compared to HISCO we have reduced the overall number of headings, while still introducing new ones, and retaining more detail from vaguely specified occupations.
In general, we made the fewest changes to the structure of the HISCO codes in major groups 0 and 1 (professional workers). We re-organized the codes within major groups 2 (administrative and managerial workers), 3 (clerical workers), 4 (sales workers), 5 (service workers), and 6 (workers in agriculture). We made the most substantial revisions in moving people between major groups in the manufacturing and transport major groups (7, 8, and 9).
In particular, we created codes for vague responses of the form "Works in [specified type of] factory," such as "Works in cotton mill." We grouped these workers with "Laborers" and titled, skilled workers in the same general industry.
We eliminated codes where HISCO made distinctions that were not consistently made in nineteenth century census data. For example, HISCO distinguished between hand and machine spinners. We found that most spinners did not specify whether they were spinning by hand or machine, more often giving information on what they were spinning (e.g., cotton, wool, silk), or a firm's name.
We introduced codes to handle vague occupations, as discussed above. We also created codes to retain linguistic and nominal distinctions above a rough frequency level. These distinctions are generally made in the fourth and fifth digit of the codes. For example, we distinguish between "Farm workers, specialisation unknown" (62110) and "Farmer's sons and other male relatives" (62113), because "farmer's son" was a numerically significant response in Canada. Both are considered part of the "Farm labourers and helpers, general farming and n.f.s" unit group (621).
Responses to the occupational questions also returned information that cannot be classified within an occupational classification scheme, such as relationship to workers, or indications of status. Please see the documentation for the variables OCRELATE and OCSTATUS.
Information on the products sold by retail workers (Major Group 4) is available in the variable PRODUCT.
Occupations were also coded into domestic occupational classification schemes in Great Britain, Norway, and the United States. See the documentation for the following variables for more information.
Comparability — General
Those who had no occupation, whose occupation was unknown, or who were too young to work are classified together under "No occupation/unknown".
For the harmonized occupational variable, OCCHISCO, a single occupational code that best fit the range of occupational titles was assigned to each multi-coded group, even if the single code was not the best fit for each and every individual occupational title within the group. OCCHISCO codes were assigned with attention to preserving the job status and general occupational activity of the original occupation. Users with particular interest in specific occupations should consult the alphabetic occupational strings or the alternative occupational source variables.
Some scholars argue that occupation and employment definitions create an additional disparity in the measurement of married female labor. Historically, occupational status was inherently somewhat ambiguous for married women, who might have considered their principal occupation "housewife" despite other labor they performed. Users should carefully examine the enumerator instructions for each census with respect to women and children, since the criteria for gainful employment and occupation to be counted changed between censuses. There are often special rules for the treatment of unpaid family labor.
In Canada 1891 and Iceland 1703, 1801, 1901 and 1911 respondents reported a primary and a secondary occupation. In Denmark 1787 and 1801, some respondents reported as many as six occupations. Only the primary occupation of respondents is coded into this variable. To identify the secondary occupation of respondents in Iceland refer to IS1703A_0420, IS1801A_0409, IS1901A_0441, and IS1910A_0407. For Canada, refer to CA1891A_0455. For Denmark, refer to DK1787A_0417, DK1787A_0418, DK1787A_0419, DK1787A_0420, DK1787A_0421, DK1801A_0413, DK1801A_0414, DK1801A_0415, DK1801A_0416, and DK1801A_0417. Users should note that the number of occupation categories reported has some variation across the Iceland samples.
- Canada: 1871, 1881, 1891, 1901
- Denmark: 1787, 1801
- Egypt: 1848, 1868
- Germany: 1819
- Iceland: 1703, 1729, 1801, 1901, 1910
- Ireland: 1901, 1911
- Norway: 1801, 1865, 1875, 1900, 1910
- Sweden: 1880, 1890, 1900, 1910
- United Kingdom: 1851a, 1861a, 1861b, 1871b, 1881a, 1881b, 1891a, 1891b, 1901a, 1901b, 1911
- United States: 1880a