[영문]The Paper briefly reviews social security coverage that the world has achieved and summarizes economic and social benefits of a national social security system. It then goes on to argue that social security systems are a necessary part of the institutional framework of any effective market economy, creating-among other things-societal cohesion that is needed for long-term economic development. It makes the case that the introduction of basic social protection in developing countries is both a desirable and an affordable investment in their social and economic development. It estimates the global minimum investment cost to provide basic social security and finally suggests international instruments to introduce a global social security floor