The population density of Tokyo is lower than that of London, and it is just one sixth that of Hong Kong. The majority of people reside in suburban areas, and 65 percent of all commutes are taken on public transportation. These facts can be attributed, at least in part, to the historical progression of the city.
Tokyo was originally composed of a large number of smaller settlements, which, over the course of its history, merged together to form a single city. At first, the communities were separated from one another by fields and rivers; later, highways and railways were built in their place. The Meiji period (1868-1912) is considered to be the beginning of suburbanization in Tokyo.
During this time, the government pushed people to move out of the city center to get away from the overcrowding and the increased risk of fire. After World War II, the population of Tokyo increased, prompting the government to build new towns in the suburbs in order to absorb the inflow of people. This caused the suburbanization process to speed up significantly.
The city center continues to have the highest population density of any portion of Tokyo, despite the fact that the greater Tokyo metropolitan area is home to nearly 35 million people today.