  A quota mechanism links together multiple decisions by imposing an aggregate
quota on the type reports across all problems. We establish a tight bound on
the ex-post decision error under quota mechanisms, for a finite number of
linked problems. With this bound, we first generalize existing asymptotic
results: as the number of decisions grows large, quota mechanisms can
asymptotically implement a social choice function if and only if it is
cyclically monotone. In this case, we also quantify the speed of convergence.
Next, we bound the decision error that results if the designer's estimate of
the type distribution is inaccurate. Finally, we show that quota mechanisms are
robust to agents' beliefs about each other.
