Do you have a table to transform the OCCHISCO variable into HISCO-codes? Or, do you have a table for creating a HISCLASS-variable from OCCHICSO?
The IPUMS variable OCCHISCO is a modified version of the HISCO coding scheme. IPUMS has made extensive changes to the HISCO scheme in order to create OCCHISCO, and harmonized IPUMS International surveys from multiple countries dating back to the 18th century into the OCCHISCO codes. 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. 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).
You can read about how IPUMS adapted the HISCO codes in more detail in the article “Occupational Classification in the North Atlantic Population Project” (2003). While I am not aware of a crosswalk between the HISCO codes and the OCCHISCO codes, you can see how the original codes in the different IPUMS International samples map on to the harmonized OCCHISCO codes by clicking “Explore how IPUMS created this variable” in the OCCHISCO codes section.