Page - (000253) - in Knowledge and Networks

249 Table 12.1 further shows the importance of normalizing the observed frequen- cies. For example, compare the pairings (1) Nature and Journal of Climate and (2) Nature and Monthly Weather Review. Both have similarly observed co-citation fre- quencies in the WOS: 2720 and 2226, respectively. However, compared to chance, the first pairing appears to have high conventionality while the second pairing seems to have high novelty. Null Model Detail The null model creates random synthetic instances of the WOS while incorporating realistic aspects of the data and its network structure. In particular, the null model incorporates two basic empirical facts about citation patterns: – Citation distributions are skewed. Some papers and journals are cited far more often than other papers and journals and consequently are referenced more fre- quently in bibliographies. – Citation counts are dynamic processes that vary by the journal (Stringer, Sales- Pardo, & Amaral, 2008), so that the rate at which papers accumulate citations is journal dependent. Keeping these facts in mind, the null model preserves for each paper in the WOS the same number of references to past work, the same number of citations from Table 12.1 Examples of journal pair frequencies for illustrative paper Journal pairs Observed Expected Z-score Mon. Weather Rev.– 28,685 68.999 3252.658 Mon. Weather Rev. Int. Journ. of Climatology– 402 0.1 1339.667 Int. Journ. of Climatology Nature–Journ. of Climate 2720 1392.016 47.344 Geogr. Anal.–Journ. of Clim. 3 2.199 0.743 A z-score of zero means the actual journal pair frequency is the same as expected by chance pairings N.Z. Journ. Geol. & Geophys.– 4 4.0 0 Journ. of Climate Nature–Aust. Meteorol. Mag. 89 95.494 −0.915 Geogr. Anal.–Mon. Weather Rev. 2 6.192 −1.436 Nature–Geogr. Anal. 30 138.889 −8.78 Nature–Mon. Weather Rev. 2226 3779.287 −24.554 Note. Mon. Weather Rev. Monthly Weather Review, Int. Journ. of Climatology International Journal of Climatology, Geogr. Anal. Geographical Analysis, N.Z. Journ. Geol. & Geophys. New Zealand Journal of Geology and Geophysics, Aust. Meteorol. Mag. Austrian Meteorology Magazine. From Uzzi et al. (2013b, p. 21). Copyright 2013 by Science. Adapted with permission from the authors and Science 12 How Atypical Combinations of Scientific Ideas Are Related to Impact:…