Critical thinking has become an essential skill required by both higher education and workforce. Prior research reported moderate learning gains in critical thinking through college. However, retention, differential participation, and students' low test-taking motivation have possibly confounded the prior conclusions. Controlling for such factors, we found a gain of 0.24 SDs after four years in college (n=2,381 students, 46 institutions), considerably smaller than previously reported results. Natural science majors performed the highest and business majors performed the lowest. Minority students achieved only half of the gain of white students. Fifty percent of minority students scored below the Proficient level, compared to 27% for white students, and only 5% performed at the Advanced level, compared to 20% for white students.