UnionMaps developed by the Wales Institute of Social and Economic Research and Data (WISERD) reveals the complex patterns in trade union membership that exist across Great Britain. This free interactive mapping tool presents estimates of trade union membership and the coverage of collective bargaining agreements for the Unitary Authority and Local Authority Districts of Great Britain: there are over 400 such areas. Simply click on the map or use the search tool to produce area reports of union membership for a particular location. Alternatively, use `Map the data’ to see how the different measures of union membership vary across Great Britain. The data displayed via UnionMaps is documented in an accompanying report and can also be downloaded via a Statistical Compendia. The data reveal that the Cumbrian coast has the highest levels of union membership in Great Britain. The decline in the North East has been notably dramatic. Visit UnionMaps to find out how high union membership is where you live and how it has changed over recent decades.