The biggest drawback is probably the fact that the central municipality's administrative boundaries can provide an inaccurate picture of the forms of urban development in a CMA. In some CMAs, people who live a dozen kilometres from the city centre, in neighbourhoods that have all the qualities of traditional suburban neighbourhoods, are nevertheless residing in the central municipality. Conversely, in other CMAs, people living only a few kilometres from the central business district, in very densely populated neighbourhoods, are regarded as living in a suburban municipality. The reason for these differences is that municipal history, and therefore municipal administrative boundaries, vary substantially from CMA to CMA. As a result, the percentage of the CMA's total population living in the central municipality as opposed to the suburban municipalities will also vary a great deal from one metropolitan area to another (Chart 1).
For example, according to 2006 Census data, Calgary's seven suburban municipalities accounted for only 8% of the CMA's total population. The same was true for the CMA of Winnipeg, where the suburban municipalities also made up only 9% of the CMA's total population. The situation was completely different in the CMA of Vancouver, where 73% of the total population lived in the suburban municipalities.
While the difference in the percentages provides some idea of the extent of administrative fragmentation in these metropolitan areas, it tells us very little about the types of neighbourhoods in which Calgary and Winnipeg residents live compared with Vancouver residents. In addition, comparing the central municipalities of the various CMAs can lead to serious misinterpretations if we fail to take into account how each one is divided.3
A second major disadvantage of the approach based on the central municipality's administrative boundaries, in terms of sociological and geographic analysis of CMA populations, is that boundaries can change abruptly at any time, especially during municipal mergers or reorganizations. Neighbourhoods and localities that had long been considered suburbs can suddenly become part of the central municipality, even though there has been no substantive change in their areas' nature or their social and economic ties to the centre.
For example, the town of Pierrefonds is now included in one of the wards of the new municipality of Montréal, although it was considered an independent suburban municipality before the municipal mergers of 2001. The same thing happened to the Borough of East York in the CMA of Toronto: before 1998 it was a suburb and today it is an integral part of the central municipality. In the Ottawa area, the former suburban municipalities of Kanata, Orléans, Gloucester, Vanier and Rockcliffe are now part of the central municipality. Of course, it is always possible that further municipal reorganizations will occur in the future, making the distinction between central and suburban municipalities even fuzzier than it is now.
Yet, despite these limitations (particularly from the perspective of comparing CMAs), the distinction between central and suburban municipalities remains, for some purposes, the most pertinent and useful way to present various statistics. It is important for decision-makers and policy-makers to have a variety of demographic and socio-economic information about the population of their own municipality as well as adjacent municipalities.
On the other hand, the approach based on the administrative or political boundaries of the central municipality is probably not the most appropriate for studying certain social, demographic and economic differences between suburban and urban neighbourhoods.