We show that the European Union's General Data Protection Regulation (GDPR) reduced data sharing online, but had the unintended consequence of increasing market concentration among technology vendors that provide support services to websites. We collect panel data on the web technology vendors...

Modern websites rely on personal data to analyze traffic on their websites and market them- selves. We study the European Union's General Data Protection Regulation (GDPR), which requires that sites seek user consent to process personal data like cookie identifiers and email ad- dresses. We...