  We provide a detailed characterization of the optimal consumption stream for
the additive habit-forming utility maximization problem, in a framework of
general discrete-time incomplete markets and random endowments. This
characterization allows us to derive the monotonicity and concavity of the
optimal consumption as a function of wealth, for several important classes of
incomplete markets and preferences. These results yield a deeper understanding
of the fine structure of the optimal consumption and provide a further
theoretical support for the classical conjectures of Keynes (1936).
