It is understood that rational expectations equilibria may not be incentive compatible: agents with private information may be able to affect prices through the information conveyed by their market behavior. We present a simple general equilibrium model to illustrate the connection between the notion of informational size presented in McLean and Postlewaite (2002) and the incentive properties of market equilibria. Specifically, we show that fully revealing market equilibria are not incentive compatible for an economy with few privately informed producers because of the producers' informational size, but that replicating the economy decreases agents' informational size. For sufficently large economies, there exists an incentive compatible fully revealing market equilibrium.