The well-being of the community as a whole. In general, economics takes this as being entirely determined by the preferences of the individuals within the society. It is not regarded as something which is inherently measurable, since, if the utility of an individual is not measurable, how can that of a group be? Rather, we can only say of any two given situations that ‘society’ prefers one situation to another or is indifferent between them. If we wish, we can then say that social welfare is greater in one situation than another or is the same, but this is not implying the intrinsic measurability of social welfare. The difficulty then is to establish criteria by which to say that ‘society’ prefers one situation to another or is indifferent between them. For a discussion of this, see socal welfare function.
Reference: The Penguin Dictionary of Economics, 3rd edt.