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253 gests very high degrees of conventionality. Half the papers had median z-scores exceeding 69.0 in the 1980s and 99.5 in the 1990s. Moreover, papers with a median z-score below zero were rare. In the 1980s only 3.54 % of papers had this feature, while in the 1990s the percentage fell to 2.67 %, indicating a persistent and promi- nent tendency for high conventionality. Focusing on each paper’s left tail combinations, we found that even among the paper’s relatively unusual journal combinations, the majority of papers did not fea- ture atypical journal pairs. Figure 12.4c shows that 40.8 % of the papers in the 1980s and 40.7 % in the 1990s had a 10th percentile z-score below zero. Overall, by these measures, science typically relies on highly conventional combinations and rarely incorporates journal pairs that are uncommon compared to chance. Our next finding indicates a powerful relationship between combinations of prior work and ensuing impact. Figure 12.5 presents the probability of a “hit” paper con- ditional on the combination of its referenced journal pairs. Hit papers are operation- alized as those in the upper 5th percentile of citations received across the whole dataset, as measured by total citations through 8 years after publication. The vertical axis shows the probability of a hit paper conditional on a 2 × 2 categorization indi- cating the paper’s (i) “median conventionality” (an indicator of whether the paper’s median z-score is in the upper or lower half of all median z-scores) and (ii) “tail novelty” (an indicator of whether the paper’s 10th percentile z-score is above or below zero). Papers with “high median conventionality” and “high tail novelty” display a hit rate of 9.11 out of 100 papers, or nearly twice the background rate of 5 out of 100 papers. All other categories show significantly lower hit rates. Papers featuring high median conventionality but low tail novelty displayed hit rates of 5.82 out of 100 papers, while those featuring low median conventionality but high tail novelty dis- play hit rates of 5.33 out of 100 papers. Finally, papers low on both dimensions have hit rates of just 2.05 out of 100. Further analyses suggest universality of these relationships for scientific work across time and fields. In Fig. 12.6, we show that the results hold (a) over five decades of data recorded in the WOS from 1950 to 2000 and (b) using the upper 1st or 10th percentiles of citation impact. In Fig. 12.7, we define the cutoff for high and low tail novelty at different percentiles of a paper’s z-score: The 1st, 5th, 20th, 30th, and 40th. Figure 12.7 shows that using the 1st, 5th, 10th, or 20th percentile captures significant positive associations between impact and tail novelty in the 1990s. Beyond the 30th percentile, the significant association between impact and tail nov- Fig. 12.4 (continued) median z-scores and shows that the vast majority of papers display a high propensity for conventionality; in the 1980s and 1990s fewer than 4 % of papers have median z-scores below 0 and more than 50 % of papers have median z-scores above 64. (c) considers the 10th percentile z-scores, which further suggest a propensity for conventionality; only 41 % of papers in the 1980s and 1990s have a 10th percentile z-score below 0. Overall, by these measures, science rarely draws on atypical pairings of prior work. From Uzzi et al. (2013a, p. 469). Copyright 2013 by Science. Adapted with permission from the authors and Science 12 How Atypical Combinations of Scientific Ideas Are Related to Impact:…