Empirical literature identifies several factors contributing to the gender gap in computer science, including belonging uncertainty and self-efficacy beliefs, the 'pipeline shrinkage' problem (the female-to-male ratio narrowing from student years into careers), gender differences in computer-task performance and motivation, and CS-education-specific barriers such as prior computing experience, lack of role models, and departmental encouragement and support. The subtopics below organize these factors as documented in the reviewed studies.