Dworkin adds that the ideal of equality of resources should be conceived as operating over time, so that if Smith is assigned a certain resource bundle including arable land and works the land so that the resource bundle increases, one does not envy Smith's augmented bundle if one could have achieved the same augmentation with the same work output but prefers not to sacrifice present consumption for future profit in this way. Dworkin adds a further twist: he affirms that personal traits such as native charm and intelligence potential and physical strength should also be regarded as resources, so equality of resources demands compensation for shortfalls in personal trait endowments. He suggests that the appropriate compensation measure would consist of hypothetical insurance markets, in which individuals equally situated, knowing the disabilities they might have and their incidence but not whether they themselves have them or not, and knowing their personal traits but not what prices their use might fetch in market trading, have the opportunity to purchase insurance against the possibility of being afflicted with disabilities or of having a trait endowment of low market value.