 Among the other concepts of fairness which have been introduced, two families are important. The first family contains principles of solidarity, which require individuals to be affected in the same way (they all gain or all lose) by some external shock (change in resources, technology, population size, population characteristics). For instance, if resources or technology improve, then it is natural to hope that everyone will benefit. The second family contains welfare bounds, which provide guarantees to everyone against extreme inequality. For instance, in the division of non-produced commodities, it is very natural to require that nobody should be worse-off than at the equal-split allocation (i.e. the allocation in which everyone gets the per capita amount of resources).