For many years, and even more so recently, Mexico City policy makers have implicitly chosen to emphasize private and semi-private forms of transportation. By tracking subsidies to private forms of transportation and measuring the lack of public investment in public transportation infrastructure, Wirth finds de facto privatization of transportation policy highly costly from a social and ecological perspective.

Wirth challenges the idea that "privatization" occurs only when public sector responsibilities are shifted to private providers. A decision by a government not to take an active public investment role in one arena (e.g. the citys metro system) may lead to a very privatized landscape of delivery (as in Mexico Citys resulting dominance of cars and mini-buses). Second, Wirth also advocates a cost-benefit analysis that includes social and environmental externality costs. He found 80% of the notorious air pollution imposed on Mexico City to be the result of private and semi-private modes of transport. In contrast, the bus and metro systems together, beyond disproportionately serving the poorer segments of the population, account for only 2.7% of air pollution.

In sum, Wirth wants local government officials to acknowledge their critical role in shaping the landscape of service delivery, as much by decisions they choose not to make as the decisions they do make.