Quick Read. Two perfectly accurate statistics about the same named city can contradict each other because they are measuring different spatial objects.

Six boundaries that people routinely collapse

• municipal or administrative city;
• continuous built-up area;
• harmonised urban centre;
• metropolitan region;
• functional commuting area;
• historical settlement or named core.

Why the error matters

Population density, GDP per person, transit coverage, housing supply and even claims about “the world’s largest city” change when the denominator changes. A model that stores only CITY_NAME → NUMBER silently loses the boundary that made the number meaningful.

Use the city estate as tests

Tokyo, Paris, Manila, Delhi, Kuala Lumpur, Colombo and Singapore all fail in different ways if administrative and functional identities are collapsed.

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