why do private businesses underproduce public goods? they are non-excludable, and so it is difficult to earn profits by producing the good. they are rivalrous, and so only one producer can supply the good. they are excludable, and so there are too few consumers available to buy the good. they are non-rivalrous, and so market power will limit output of the good. they are non-affordable, and so there are no consumers willing to purchase the good.