Comment: Pages 32, 11 tables, 3 figureKnowledge generated in a given scientific domain may spill over into other close scientific disciplines, thereby improving performance. Using bibliometric data from the SCImago database drawn from a sample of 174 countries, we implement a measure of proximity based on revealed comparative advantage (RCA). Our estimates show that proximity between disciplines positively and significantly affects the RCA growth rate. This impact is larger on disciplines that currently do not have RCA.