Capturing government policy on the left-right scale: evidence from the United Kingdom, 1956-2006

The left-right scheme is the most widely used and parsimonious representation of political competition. Yet, long time series of the left-right position of governments are sparse. Existing methods are of limited use in dynamic settings due to insufficient time points which hinders the proper specification of time-series regressions. This article analyses legislative speeches in order to construct an annual left-right policy variable for Britain from 1956 to 2006. Using a recently developed content analysis tool, known as Wordscores, it is shown that speeches yield valid and reliable estimates for the left-right position of British government policy. Long time series such as the one proposed in this article are vital to building dynamic macro-level models of politics. This measure is cross-validated with four independent sources: (1) it compares well to expert surveys; (2) a rightward trend is found in post-war British government policy; (3) Conservative governments are found to be more right wing in their policy outputs than Labour governments; (4) conventional accounts of British post-war politics support the pattern of government policy movement on the left-right scale.