 A major shift in nearly all aspects of natural language processing began in the late 1980s and was virtually complete by the end of 1995: this was the shift to corpus-based, statistical approaches (signalled for instance by the appearance of two special issues on the subject by the quarterly Computational Linguistics in 1993). The new paradigm was enabled by the increasing availability and burgeoning volume of machine-readable text and speech data, and was driven forward by the growing awareness of the importance of the distributional properties of language, the development of powerful new statistically based learning techniques, and the hope that these techniques would overcome the scalability problems that had beset computational linguistics (and more broadly AI) since its beginnings.