Principle put forward by Italian economist Vilfredo Pareto (1848–1923) in his Manual of Political Economy (1906, trs. 1972). Put in terms of preferences, this is the principle that (i) if everyone in a society is indifferent between two alternatives then the society should be indifferent as well, and (ii) if at least one individual prefers x to y, and everyone else regards x as at least as good as y, then the society prefers x to y. When (ii) is satisfied x is Pareto-wise better than y, or a Pareto improvement over y. A choice is described as Pareto optimal if there is no alternative that is Pareto-wise better; that is, there is no alternative that everyone will regard as at least as good, and which at least one person will regard as better. The principle can also be stated in terms of wellbeing rather than preferences. Whether the Pareto principle delivers a social welfare function clearly depends on how unanimous the members of the society are. The great advantage of Pareto optimality is that no interpersonal comparisons of utility are needed in the application of the principle; it therefore avoids problems connected with the strength of preferences. The weakness of basing policy on the principle is that it tends to favour the status quo, since only one dissent is sufficient to prevent a change from being a Pareto improvement. An extension of the Pareto principle is known as the Kaldor-Hicks principle, which allows that an improvement for some can be allowed even if others are made worse off, provided that the overall benefit is sufficient to compensate the losers and more. Unfortunately in the real world, nearly all social change happens without this compensation actually being paid.