1 This chapter synthesizes research on women in STEM undergraduate fields and aims to sharpen our empirical and theoretical frameworks for future higher education research. Institutional research implications are discussed here and throughout the volume. Conceptualizing the Field: Higher Education Research on the STEM Gender Gap Lara Perez-Felkner In recent decades, and especially in recent years, significant attention has been paid to the gender gap in Science, Technology, Engineering, and Math- ematics (STEM) undergraduate education. Efforts to understand the STEM gender gap extend back over four decades, revealing a vast but evolving literature on the roots of such underrepresentation (Bottia, Stearns, Mickel- son, Moller, & Valentino, 2015; Kanny, Sax, & Riggers-Piehl, 2014). There are far fewer women than men in many key STEM fields, such as engi- neering and computer science (National Science Foundation, 2017). Impor- tantly, studies have revealed college degree field contributes significantly to the gender wage gap (Bobbitt-Zeher, 2007). Notably, computer science and engineering are among those fields with the highest economic returns to education (Corbett & Hill, 2015) as well as cognitive learning gains (Arum & Roksa, 2011). There are three critical shortcomings with higher education and broader scholarship on the gender gap in STEM. First, it too often aggre- gates all STEM fields together. This monolithic approach hinders our understanding of how women’s representation varies across different STEM sub-fields, and—perhaps more importantly—why it varies (Ganley, George, Cimpian, & Makowski, 2018; Schneider, Milesi, Perez-Felkner, Brown, & Gutin, 2015). National Science Foundation (2017) data indicates there is wide heterogeneity within the still persistent STEM gender gap; women’s represent only 18% of degree earners in computer science, 20% in engi- neering, and 40% in the physical sciences. Second, scholars insufficiently attend to how women’s experiences in STEM may be further shaped by NEW DIRECTIONS FOR INSTITUTIONAL RESEARCH, no. 179 © 2019 Wiley Periodicals, Inc. Published online in Wiley Online Library (wileyonlinelibrary.com) • DOI: 10.1002/ir.20273 11