Conventional planning wisdom suggests that suburban sprawl is the result of land use planning policies- either not enough planning or the wrong kind of planning. But Blais focuses on another cause: "mis-pricing": distortions that make urban land more expensive and suburban land less so, whether in the realm of taxes, government charges for development, or charges by private utilities.
Blais's strongest example is the development charges (also known as "impact fees") that North American charge for new development. These fees force developers to pay some of the costs associated with new development, such as the costs of new roads and sewer networks. But these charges are equal for urban and suburban locations, even though development in newly developing areas often requires more new infrastructure, and thus cost taxpayers more, than more intense development in areas that already have roads and sewers. Thus, location-neutral development charges underprice development of newer suburbs and overprice infill. Similarly, regulated utilities are often as expensive in compact areas as in sprawling suburbs, even though the latter areas require more wires and other mechanical equipment.
However, I am not sure how much these pricing issues matter. Blais seems to be focused on Canadian cities where urban locations are desirable and expensive, causing the middle class to be priced out of the urban market. But in America's Rust Belt, urban homes are usually cheaper than suburban homes. And because cities and suburbs tend to be in different municipalities, development charges are less likely to be identical. Nevertheless, Rust Belt urban areas have decayed more rapidly than their Sun Belt or Canadian counterparts.