Final answer:
Year books were used to compile the most important decisions each year as courts and cases proliferated, contributing to the development of common law.
Step-by-step explanation:
As the number of courts and cases increased, the most important decisions of each year were compiled in e. year books. The common law, also known as case law or precedent, plays a crucial role in this process. It is a system of law that emerges from judges' decisions in courts that set precedents for future cases. Historical records like Sir Matthew Hale's comprehensive look at English common law or Blackstone's Commentaries on the Laws of England helped give substance to the common law by collecting and organizing these judicial conclusions. Year books were predecessors to modern legal reports, documenting important legal decisions that could influence later rulings.