The first step in the systematic study of policy instruments, as in any other similar endeavour in the social sciences, is the establishment of an inventory of the dependent variable. While there were many scholars who had looked at specific tools in the past (such as Cushman’s 1941 study of regulatory agencies which was often cited by early students of the field), the first efforts to systematically define the range of possible instruments which could be used in a policy design originated in the post-World War II planning exercises undertaken by the United Nations and the Organization for Economic Co-operation and Development (OECD) in Europe.
Key figures in this research included Nobel Prize winning development economists such as E. S. (Etienne) Kirschen and Jan Tinbergen, who published groundbreaking studies including Economic Policy in Our Times (1964) dealing with the instruments for economic policy they had viewed in operation in the process of post-war European reconstruction. One of the first inventories of instruments was Kirschen et al.’s (1964) identification of well over forty different types of implementation instruments then prevalent in European economic policy-making activities, ranging from public enterprises to various forms of government procurement and tax incentive and subsidy schemes. Such studies were followed by many others examining the instruments prevalent in other areas, such as banking and foreign policy (Hermann 1982), adding to the list tools such as interest rate determination and other monetary and fiscal tools. These were pathbreaking studies which, although they did not make any distinctions between general implementation preferences, policy mechanisms or calibrations, and very often confused implementation tools and instruments used at other stages of the policy process, laid the groundwork for such future refinements by providing the raw data required for later classification efforts.