Copyright law was enacted rather late in German states, and the historian Eckhard Höffner argues that the absence of copyright laws in the early 19th century encouraged publishing, was profitable for authors, led to a proliferation of books, enhanced knowledge, and was ultimately an important factor in the ascendency of Germany as a power during that century. However, empirical evidence derived from the exogenous differential introduction of copyright in Napoleonic Italy shows that "basic copyrights increased both the number and the quality of operas, measured by their popularity and durability".