While the role of consultants in the policy process has long been a concern for scholars of public administration, public management and political science, empirical studies of policy-related consulting are scarce, with little quantitative data. The country-level case studies in this book shed light for the first time on a number of important but as yet under-researched questions. The first is the actual extent of the use of government consulting in a number of countries, and what have been cross-time developments: to what extent has the use of consultants grown over time, and what are the (political, fiscal-economic, society, policy-related) factors that explain greater or lesser growth in a particular country or sector? The second is the question of what role(s) consultants play in the public sector and how large is the share of these consultants in policy work (policy analysis, policy advice, implementation and evaluation).