This chapter begins with a general discussion of potential data types in variationist linguistics. Next, we present the two main data sources we use in the study: the International Corpus of English (ICE) and the Global Corpus of Web-Based English (GloWbE). The former comprises a set of parallel, balanced corpora representative of language usage across a wide range of standard national varieties. Each ICE corpus contains 500 texts of 2000 words each, sampled from twelve spoken and written genres/registers, totaling approx. 1 million words. GloWbE contains data collected from 1.8 million English language websites – both blogs and general web pages – from twenty different countries (approx. 1.8 billion words in all). Discussion of the corpora is followed by a detailed description of the data collection, identification, and annotation procedures for our three alternations. Here we carefully define the variable context for each alternation, and outline the methods for coding various linguistic constraints that are included in our analyses.