Myriads of data, a host of methods, but no single universal indicator. The Performance of Veterinary Services (PVS) Gap Analysis helps to quantify the needs of national Veterinary Services. In a world of scarce public financial resources and heightened transparency and accountability, official Veterinary Services (national Veterinary Authorities) must be able to justify their needs in economic and budgetary terms to their line minister, national parliament and the public at large, or in negotiations with donors. Animal health and Veterinary Service activities are a global public good. It is the responsibility of governments to maintain animal health systems, including networks for the surveillance and control of animal diseases to ensure the early detection of suspected animal disease outbreaks, a rapid response and, where possible, eradication of animal disease outbreaks 'at source'. The establishment of animal health systems is a core responsibility of the State, and it requires the use of public funds, although it does not preclude public-private partnerships and strategies for ensuring complementarity between the partners concerned. The PVS Gap Analysis mission of the World Organisation for Animal Health (OIE) is a method for analysing and quantifying disparities between a baseline situation (determined by PVS Evaluation using the OIE PVS Tool) and the target levels set by the country itself in accordance with its priorities. An added advantage is that the method can be used for training and awareness raising.