In economics the term ‘trade-off’ is expressed as opportunity cost, referring to the most preferred alternative given up. A trade-off, then, involves a sacrifice that must be made to obtain a certain product, rather than other products that can be made using the same required resources. For a person going to a basketball game, its opportunity cost is the money and time expended, say that would have been spent watching a particular television program (Wikipedia). Another key word is ‘sustainable development’. Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs (World Commission on Environment and Development). Sustainable development was added as one of the general objectives of the World Trade Organization when it was established in 1994.