This paper examines the impact of departmental policy changes on the trend in DFW proportions for introductory calculus at a large research university, where DFW denotes the proportion of students receiving a grade of D, F, or withdrawing from the course. We defined three distinct policy periods: Traditional (2002-2005), Active Learning (SCALE-UP) (2006-2013), and Return to Traditional (2014-2016). Regression analysis showed DFW proportions were increasing during the Traditional period, significantly decreased after the switch to SCALE-UP, remained fairly consistent during the SCALE-UP period, and then significantly increased during Return to Traditional. Individual trends for D, F, and W proportions were also analyzed. The two policy changes had the greatest influence on the trend in F and W proportions. Potential factors that could influence a student to withdraw from the course were examined. Students who withdrew had midterm averages similar to students who failed the course during the SCALE-UP period, but their averages were significantly lower than the F students during the Return to Traditional period.