Birthday + Gender + Zip code can uniquely identify anyone in the United States with 87% accuracy (Research by Dr. Latanya Sweeney). Dr. Sweeney is now a professor at Harvard University and director of their data privacy lab.

L. Sweeney. Simple Demographics Often Identify People Uniquely. Carnegie Mellon University, Data Privacy Working Paper 3. Pittsburgh 2000.

Comprehensive research and reporting about the data collection marketplace, including: 

Corporate Surveillance in Everyday Life. How Companies Collect, Combine, Analyze, Trade, and Use Personal Data on Billions. A Report by Cracked Labs, Vienna, June 2017. Author: Wolfie Christl. Contributors: Katharina Kopp, Patrick Urs Riechert. Illustrations: Pascale Osterwalder. Web link here.

Statistics about the reach of Oracle’s data marketplace: “includes more than 30,000 data attributes on two billion consumer profiles” — taken directly from Oracle press release published in 2017. Press release has been removed but archived version available here:

Examples of Additional "linking services" that match online data to offline, real-world data: 

Full reference list is also available upon request.