Critical thinking has become an essential skill required by both higher education and the workforce. Research to date has reported moderate cross-sectional learning differences in critical thinking as students progress through a 4-year college. However, retention, differential participation, and students' low test-taking motivation possibly confounded conclusions from prior studies. Controlling for such factors, we found a cross-sectional difference of 0.24 SDs after 4 years in college (n = 2,381 students, 46 institutions), considerably smaller than what's reported in prior studies. Natural science majors performed the highest and business majors performed the lowest. Minority students achieved only half of the cross-sectional difference (0.18 SDs) of white students (0.39 SDs), and only 6% of them scored at the Advanced level, compared to 24% of white students.