We study asset markets and wealth dynamics in the economy with heterogeneous beliefs and risk of default. Agents can trade a full set of Arrow securities but are allowed to default on their delivery promises. Financial markets rationally subject agents to the endogenous “no-default” borrowing limits. Because of the rich menu of financial assets traded in the market speculation opportunities are plentiful. Financial wealth is volatile and the endogenous borrowing limits are always active. Variance of the asset returns is amplified. The asset trading volume is substantial and volatile.

In a model with multiple Pareto-ranked equilibria, we show that the set of equilibria shrinks if we allow trade in assets that pay based on the realization of a sunspot acting as an equilibrium-selection device. When the probability of a low-output outcome is high, the desire to insure against it leads the poor to promise large transfers to the rich in the high-output state. The rich then lose the incentive to exert the effort needed to sustain the high output. Thus the opening of financial markets may destroy the high equilibrium.

We compare market prices of risk in economies with identical patterns of endowments, priors, and information flows, but two different market structures, one with complete markets, another in which consumers can trade only a single risk-free bond. We study how opportunities to speculate, uncommon priors, and learning affect market prices of risk. Two types of consumers have diverse beliefs about the law of motion for a random exogenous endowment. One type knows the true law of motion while the other type learns about it via Bayes' theorem. Less-well-informed consumers are pessimistic, initially overestimating the probability of a catastrophic state. Learning dynamics and the wealth dynamics that they drive contribute to differences in evolutions of market prices of risk across market structures.