It has been indicated that the post office may be conducted with a number of ends in view. The same may be said of public industries in general. The revenue aspect first held an important place, such as it still holds in the tobacco and salt monopolies of some European countries. The general trend, however, has been to emphasize the service aspect, and with this in mind net revenues have often disappeared, and deficits have to be made up from the general fund. Such a situation does not indicate that the conduct of the industry has been a failure, because success is not always to be measured in financial returns. The postal system of the United States must be considered a success in that it has been a factor for the cheap dissemination of information, even though there has been a financial deficit.

Highways were once conducted with the idea of getting at least some return, yet the public tollgate is an institution that most members of the younger generation have never seen. The maintenance of highways, moreover, is not branded as a failure because no revenue, gross or net, is received. Municipal waterworks, while they have never been conducted on the same principle as highways, frequently tend in this direction. Deficits often occur, not because the enterprise could not be made financially successful, but because the aim in view has been to give a service at a low cost. In measuring the success of a public industry, then, the aim with which it is conducted must always be considered. In most cases the fiscal aim has been superseded by the desire to give a public service.