Health Care Manag Sci DOI 10.1007/s10729-016-9379-x Forecasting the medical workforce: a stochastic agent-based simulation approach M´ ario Amorim Lopes 1 · ´ Alvaro Santos Almeida 2 · Bernardo Almada-Lobo 1 Received: 13 February 2016 / Accepted: 22 August 2016 © Springer Science+Business Media New York 2016 Abstract Starting in the 50s, healthcare workforce plan- ning became a major concern for researchers and policy makers, since an imbalance of health professionals may create a serious insufficiency in the health system, and even- tually lead to avoidable patient deaths. As such, methodolo- gies and techniques have evolved significantly throughout the years, and simulation, in particular system dynamics, has been used broadly. However, tools such as stochas- tic agent-based simulation offer additional advantages for conducting forecasts, making it straightforward to incor- porate microeconomic foundations and behavior rules into the agents. Surprisingly, we found no application of agent- based simulation to healthcare workforce planning above the hospital level. In this paper we develop a stochas- tic agent-based simulation model to forecast the supply of physicians and apply it to the Portuguese physician work- force. Moreover, we study the effect of variability in key input parameters using Monte Carlo simulation, conclud- ing that small deviations in emigration or dropout rates may originate disparate forecasts. We also present different sce- narios reflecting opposing policy directions and quantify  M´ ario Amorim Lopes mario.lopes@fe.up.pt ´ Alvaro Santos Almeida almeida@fep.up.pt Bernardo Almada-Lobo almada.lobo@fe.up.pt 1 INESC-TEC Porto, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal 2 CEF-UP, Faculdade de Economia da Universidade do Porto, Porto, Portugal their effect using the model. Finally, we perform an analy- sis of the impact of existing demographic projections on the demand for healthcare services. Results suggest that despite a declining population there may not be enough physicians to deliver all the care an ageing population may require. Such conclusion challenges anecdotal evidence of a sur- plus of physicians, supported mainly by the observation that Portugal has more physicians than the EU average. Keywords Healthcare workforce planning · Agent-based simulation · Health economics · Monte Carlos analysis 1 Introduction Health care delivery is a labor-intensive sector, composed of physicians, nurses, clinical assistants and other adminis- trative staff. Imbalances in the supply of human resources delivering health care services are known to cause severe economic and social harm [4], and may ultimately lead to patient deaths [52]. Concern has been growing over a future lack of human resources for health [49], and the United Nations has included this pressing problem in their Millennium Development Goals [21]. It is not an isolated problem, as a lack of medical staff in developed countries may divert scarce resources from developing countries. As a result, several health authorities and academic institutions have been addressing this problem. The work hereby pre- sented is part of one such initiative, the EU Joint Action on Healthcare Workforce Planning and Forecasting. One of the main goals is to develop a robust model to forecast the evolution of the medical workforce. The first step was to consult the literature. After reviewing over 60 years of research in the field to understand how it evolved in terms of methodologies and its current state [4], we noted that no