sentences:  The Statistics Bureau of Japan (SBJ) defines a metropolitan area as one or more central cities and its associated outlying municipalities.To qualify as an outlying municipality, the municipality must have at least 1.5% of its resident population aged 15 and above commuting to school or work into one of the central cities.To qualify as a central city, a city must either be a designated city of any population or a non-designated city with a city proper population of at least 500,000.