1. A system for detecting statistical variations in public opinion comprising: a plurality of response interfaces for capturing opinion values of a set of respondents in relation to a subject matter, each opinion value having a respective validity period associated therewith; a database in communication with the plurality of response interfaces, the database including a plurality of data structures for storing each opinion value corresponding to each respondent and to said subject matter; a statistical processing unit in communication with the database for calculating an opinion output from subsets of each opinion value according to each respective validity period.