The physical extent of Metropolitan Manila today has expanded far beyond the Manila and suburbs that we knew two or three decades ago. As a matter of fact, almost everyone has his own concept of what Metro Manila is.
The Bureau of the Census and Statistics (BCS) has defined Metro Manila as composed of the following four cities: Manila, Quezon City, Pasay and Caloocan; and four municipalities: Makati, Mandaluyong, San Juan, and Paranaque. As we are all aware, this is indeed a very limited definition.
The National Waterworks and Sewerage Authority, in collaboration with two international engineering firms working under United Nations Special Fund assistance agreed on the practical limits of water and sewerage services for defining Metro Manila "based on topography and land use."
Encarnacion has identified eleven different ways to define Metro Manila. Each is geared to a specific purpose and based on a different set of criteria. The BCS--'OSCAS definition which includes the City of Manila plus the ring of administrative units touching it, is the officially accepted version. Thus, it excludes the town of Parafiaque, which does not touch Manila, and includes instead, the town of Navotas which is adjacent to Manila. This area is now termed as "Manila and Suburbs".
What is the scope of the Metropolitan Area? There seem to be many answers to this question, depending on the varied purposes and criteria. Even elsewhere in the world there is no agreement as to what a metropolis really is.