The preceding chapter demonstrates the richness as a resource for comparative time-series analysis of the estimates made by the Manifesto Research Group (MRG). There is currently no other data set that records the policy positions and movements of central political actors over so many countries and time points. The best that other attempts (for example, the expert surveys of Castles and Mair 1984; Laver and Hunt 1992) can offer are problematic locations of parties, at one point in time, that cannot be compared unambiguously with locations in other countries or years. Analyses of texts have the advantage that they are concerned with statements of policy made at a particular place and time by a specific person or organisation. They therefore avoid the problems associated with expert judgements of party positions, which estimate policy positions at least in part from the actual behaviour they are designed to explain. Such surveys can also be ambiguous about the time period involved, the criteria used to locate actors and the precise identity of the actor being located (Budge 2000; Huber and Inglehart 1995). The same criticism might be raised against using electoral perceptions of party policy positions (Gabel and Huber 2000).