Calling all Demographers

Double posted from here.

So, i’m fiddling with some citation data for a few Demography journals,* and came up with a couple of weird data points that i can’t account for, so thought i’d see what teh intertubes could tell me about it. Basically, early in the process of working with this sort of data, I like to take a look at “Citation Age” information.** This gives a sense of how old the literature is that people are drawing on in a given time period. These often roughly follow linear increases (though the rate of “aging” differs across fields). Anyway,  this one presented a couple of pretty extreme outliers (i’ve done this more than just a couple of times, and haven’t seen others this different). I can’t account for them, so am looking for any potential explanations.

Unfortunately the data isn’t currently in a format that would let me actually “solve” what’s accounting for this, but i should be able to soon, so it could be fun to see whose/which theories hold up. Anyway, if looking at this information by year, 1988 and 1991 are considerable outliers (see the plot after the jump). It would appear that most of the “blip” in 1988 comes from increased citations to work roughly 50 years before, while the one in 1991 comes from citations to work roughly 70 years earlier. Given that i’m not a “full fledged” demographer (training-wise), i’m guessing others of you might be able to help me out here. What happened in 1988 that led people to suddenly read/cite work from the 1930s and from 1991 to suddenly read things from the 1920s***? All potential explanations welcome.

Citation Age (in PDR, Dem, PRPR & PS) 1983-2012

_________

* This currently includes DemographyPopulation StudiesPDR and PRPR. I’m happy to quibble with this definition of the “general” demography journals, and am definitely open to other suggestions. However, i think that’s likely a slightly separate question. I did initially aim to also include Demographic Research, but ISI (my main data source) didn’t start indexing that until 2005, so its considerable censoring made keeping it seem wonky.

** There are lots of different ways to compute “citation age” and after discussing this more times than those who work with me on these things would like, we’ve settled on typically using the option that basically depends on single cited-citing pairs contributing one observation (not a unique cited papers list, nor a citing paper-wise average). We think the others could be interesting, but for answering questions other than those we’re typically after.

***So far, we have one theory for the 1991 one which i’m looking into.

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7 Responses to Calling all Demographers

  1. Cool puzzle jimi! I wonder if a special journal volume dedicated to something which requires older references could pull the means up like that.

    • jimi adams says:

      Yeah, special issues are definitely potentially important especially for things like this. That doesn’t appear to be accounting for these two cases. There’s only one i see explicitly as a “stand alone” special issue in either of those years – on British Demography which doesn’t appear to be accounting for the 1991 blip (the citation ages from those papers are actually younger than the over-represented slice from the 20s, i.e., didn’t seem to be doing much to shift the distribution). So more “hidden” symposia are what i’m hoping to dig up.

  2. PAA was founded in 1931, making 1991 the 70th anniversary and probably accounting for that outlier. I know that there are a couple of review papers addressing this (e.g., Hodgson’s PDR paper on the ideological origins of PAA) and such. Review papers can definitely skew citation statistics so a year where there are several of them, all citing documents surrounding the founding of the association may be driving it. Not so sure about 1988…

    • jimi adams says:

      The 1991 blip definitely is coming from before 1931. Closer to the teens and early 20s. I’m guessing those years would help point you to the story i’m currently trying to dig through.

  3. But those are possibly the years that are going to inform the founding of the association, no?

    • jimi adams says:

      Yeah, i missed your point the first time. That paper in PDR may go a long way to accounting for that blip (needed an excess ~100 papers with citations in the 20s). I had been hoping it was something (more interesting?) like HIV researchers who were citing the 1918 flu epidemic.

  4. Or it could just be that there’s a single citation to “Plato. -380. Πολιτεία.” or something.

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