If I had to write one of those snappy back cover blurbs for this book, I might go with “a book written by a law geek for other law geeks”. I first encountered and began conducting empirical studies of large sets of legal materials about six years ago. Ever since I began working on my doctoral thesis, I have had one foot in constitutional law and particularly the constitutional law of the European Union. Researching EU law inevitably involves sifting through a substantial number of decisions by the Court of Justice, searching for patterns and meaning that are sometimes rather obscure. It has therefore been very exciting to discover, together with my friend and colleague Mattias Derlén, that methods commonly used in other research fields provide great assistance when exploring the proverbial haystack. Through this process, I have become a great believer in the promise of exploring legal questions and legal assertions using real-world data, an approach to legal research that is frequently referred to as empirical legal studies.