Variation studies is an increasingly popular area in linguistics, becoming embedded in curriculum design, conferences, and research. However, the field is at risk of fragmenting into different research communities with different foci. This pioneering book addresses this by establishing a canon of state-of-the-art quantitative methods to analyze grammatical variation from a comparative perspective. It explains how to use these methods to investigate large datasets in a responsible fashion, providing a blueprint for applying techniques from corpus linguistics, variationist, and dialectometric traditions in novel ways. It specifically explores the scope and limits of syntactic variability in a global language such as English, and investigates three grammatical alternations in nine varieties of English, exploring what we can learn about the grammatical choices that people make based on both observational and experimental data. Comprehensive yet accessible, it will be of interest to academic researchers and students of sociolinguistics, corpus linguistics, and World Englishes.