We measure the impact of retail externalities on the productivity of stores in shopping malls. We focus on (1) retail externalities generated by anchor stores, and (2) retail externalities generated by competing stores. We identify these retail externalities using variations in the composition of stores within shopping malls over time. We use monthly sales data from 1,170 stores that were located in 9 Turkish shopping malls over 2013-2016. We find evidence for anchor and competition externalities within shopping malls. Both externalities show distance decay effects within the shopping malls. We also find considerable heterogeneity in the impact of the two retail externalities and their distance decay effects across stores from different product categories.