Consider a situation when we need to transport water from one place to another place in a leaky bucket. Some of the water would always leak out. If all water leaked out, it is obvious that we would stop our efforts to carry water. Our decision to carry the water or not will depend on how leaky the bucket is and on how big is our need for water at the destination. For instance, if bringing a little water to the other end can save a life we will be perhaps willing to accept that, say, 99 % of the water leaks out. This is an extreme situation. Societies, however, tacitly judge how much leakage they are prepared to tolerate while making a transfer to the needy. (...)