Privacy regulation and online concentration during demand peaks: evidence from the E-commerce sector

In this paper, we study how the introduction of the GDPR affected online traffic and concentration. We rely on a unique dataset collecting information on websites' visits in the E-commerce sector, and we implement a difference-in-differences model that exploits the geographical origin of website traffic. We classify websites according to their pre-GDPR amount of visits to capture potential heterogeneous effects based on websites' size. We exploit the advent of the 2018 Black Friday to assess how online consumption and concentration react in a period of demand peak when constrained by privacy regulation. Our findings show that (1) online traffic decreases after GDPR, (2) the impact is higher for small websites which however gain traffic during demand peaks, and (3) online concentration decreases in Germany but increases in Italy.