IPUMS has its own algorithm for calculating the NPB SES index for decennial censuses (and now ACS). As part of a Florida State University project to document the NPB index and its evolution over time, I need to consult with the IPUMS staff about the details of this algorithm and how it has been applied to the historical sequence of IPUMS data sets. Please contact me at ecarlson@fsu.edu to assist with this project. Thank you.
IPUMS USA provides documentation for composite measures of occupational standing variables in this user note as well as in the documentation for individual variables (e.g., NPBOSS50, NPBOSS90, SEI). Our user support team is happy to answer any questions that you have about these either on the forum or over email at ipums@umn.edu.
Thank you, Ivan. I previously studied the user note and other documentation. I have specific questions about the algorithm used by IPUMS for the described calculations.
First, for calculating the median income and median education for persons in each occupational category, what is the universe of persons considered? Traditionally the NPB index has referred to persons in the “experienced labor force” over age 14. What IPUMS variable(s) are used to identify this “experienced civilian labor force?” Has this definition of the labor force/universe for measuring education and income been used consistently in calculating NPB values for past censuses?
Second, in the original NPB values for 1950 through 1970 (or perhaps 1980) only heads of household were considered in calculating distributions of income and education; other members of their households were assigned the NPB scores of the household heads. Am I correct that IPUMS follows the practice from 2000 and subsequent scores, considering all individuals in the experienced labor force rather than just household heads? If so, are the baseline distributions of income and education determined for both sexes combined and then medians calculated for occupations without regard to sex of individual workers, rather than considering distributions separately for men or women? Are NPB scores for persons outside the experienced civilian labor force therefore “missing values?” (This question is related to the first one above—for past historical censuses such as 1960 and 1970, does the considered universe include all persons in the experience civilian labor force rather than only household heads?)
What level of detail/disaggregation was used by IPUMS in identifying separate occupational categories to be ranked by median income+education? What variable/codes were used to create these occupational categories for ranking?
Thanks for any details you can furnish about these IPUMS calculations! We aim to document such details in hopes of encouraging wider use of the NPB scores by contemporary researchers. Charlie Nam himself is looking forward to hearing about these calculations. I look forward to any assistance you and your colleagues might be able to offer.
Regards,
Elwood Carlson
Center for Demography and Population Health
Florida State University
Dear Ivan,
Following up on my previous response to your email (below), I would like to ask whether it might be possible to communicate directly with someone who does the actual coding of the NPB scores for ACS data. Charles Nam himself is approaching his 100th birthday, and we at Florida State University are working on a project to revitalize and encourage use of the NPB index scores in IPUMS. This includes and effort to make transparent to interested scholars exactly how the coding of this variable proceeds. We’d like to know what kind of programming language is used for the coding, the variables and codes involved, you get the idea! Thanks for any help in putting me in touch with the appropriate IPUMS staff members!
Yours truly,
Elwood Carlson
Center for Demography and Population Health
Florida State University
It’s great to hear that there is a project encouraging wider use of the NPB scores! The researcher who wrote the code for these variables is no longer at IPUMS, but if you email us I can share more information such as our code for generating the variables and our internal process documentation.
We note in the description tab for NPBOSS90 that the “scores were based on the earnings and education levels of the employed civilian labor force aged 16 and above, excluding persons who did not work in the past one year.” This latter condition restricts the median calculation to the experienced labor force, which is identified with WORKEDYR (worked last year) = “yes” in all samples except in 1950 where WKSWORK1 (weeks worked last year) > 0 is used instead.
You are also correct that IPUMS considers all individuals in the experienced labor force rather than just household heads. It is also the case that medians are calculated by occupation without regard to the sex of individual workers. While only data on persons in the experienced civilian labor force is used to construct the scores, all persons with a recorded occupation are assigned their occupation’s score. In samples from 1960-onward, occupation information is available for many people who were not working at the time of the census. In 1960 and 1970, occupations were reported for persons who had worked within the previous ten years. From 1980-onward, occupations were reported for persons who had worked within the previous five years. In these cases, the occupation that the respondent worked in their most recent job was recorded. Researchers who wish to exclude currently unemployed persons from their analyses can use the LABFORCE variable to do so.
NPBOSS90 uses occupation groups in the IPUMS harmonized occupation variable OCC1990, while NPBOSS50 uses OCC1950. These harmonized occupation variables are created by IPUMS from the original occupation data to provide researchers with a consistent classification of occupations across time. Extensive documentation on how these variables were created is available in the variable description tabs as well as in the integrated occupation and industry codes user note.
Now we are getting somewhere! Your email below contains much of the detail that I have been looking for. I will explore this information using a couple of the samples I’ve downloaded. In order to experiment with replicating the IPUMS calculations, a look at the actual code used for generating the variables would be extremely helpful. Is my request in this email sufficient to enable you to attach such information, or do I need to contact another separate email address? We’re grateful for your assistance and look forward to future communications as we work on these variables and stimulate interest in NPB scores. I’m copying Charlie, Mary and Monica on this email so they will be in the loop as we move forward.
Our exchange thus far has been through the IPUMS forum. You can email our user support team directly at ipums@umn.edu.