All think tanks are subject to criticisms for their choice of datasets and classifications, and the conclusions they reach as a result of these decisions.  

At the Centre for Cities, it is our preference for using Primary Urban Areas (PUAs) to define cities that occasionally draws ire. In this vein, Paul Wheeler's recent piece (‘It's Not That Grim up North') questioned the ongoing effectiveness of PUAs as a framework for understanding the changes that have taken place in UK cities, and particularly Manchester, over the past decade.