With 75,000 people per square kilometer, Delhi is over three times more densely populated than London at its peak. And it's clearly visible how big is Tokyo compared to London and to other cities in our world. Cities do not stay the same. They change and adapt throughout time, just like living beings. In reaction to economic, political, and environmental changes, some expand while others contract. However, they do so in quite varied ways, reflecting local reactions to regional, national, and global changes.

LSE Cities recently focused on the growth, governance, transportation, and density patterns of the four national capitals of Japan, India, Colombia, and the United Kingdom. Tokyo, Delhi, Bogotá, and London have a combined population of almost 80 million people (equivalent to Germany's population) and a combined GDP of $2. 2 trillion, or three times the size of the Brazilian economy, according to the Brookings Institution. In the previous four decades. Tokyo has evolved into a highly efficient global megacity – however, despite its renowned integrated public transportation system and the 2020 Olympics, the city is expected to lose 400,000 residents over the next 15 years due to low birth rates and a declining national economy. London, on the other hand, has recently emerged from the demographic doldrums, surpassing its historic high of nearly 8.6 million people (its population in 1939) and riding high on its worldwide economic drawing power (it recently topped the Mori Memorial Foundation's city'magnetism' rating). Growth is fueled by a dynamic birth rate (twice that of Rome or Madrid) and high in-migration drawn to London's resilient economy, which is aggressively promoted by its proactive mayors. With a population of just less than 8 million people, Bogotá, Colombia's capital, has built on the wise policies of successive mayors to deal with typical Latin American trends of informality, violence, and uncontrolled expansion. Bogotá, along with Medelln, is seen as a regional paradigm on how to manage urban development, having introduced the Transmilenio Bus Rapid Transit and a huge system of cycleways (ciclovas, which predate Boris bikes by a decade). Despite being the capital of the world's largest democracy, or perhaps because of it, Delhi continues to struggle to find a political voice. Despite being one of the safest megacities in the world, with 2. 7 homicides per 100,000 people compared to Bogota's 16. 1, the metropolitan area of more than 23 million people has seen a sharp increase in inequality, despite the former chief minister's pioneering efforts to build a metro system and introduce natural gas to its buses and rickshaws. The 'fit' between the size of the administrative boundaries governed by a city mayor or governor and the actual number of people who live in the 'wider functional metropolitan' area is at the center of current discussions concerning the efficiency of urban governance. As cities' populations and footprints have grown over time, they have spilled into many political jurisdictions, resulting in fragmented decision-making and lack of coordination, despite the fact that they all 'belong' to a continuous metropolitan agglomeration. Only seven million of Mexico City's 22 million citizens are actually under the supervision of the city mayor of the Distrito Federal, whereas the majority of the population lives (and pays taxes) in the surrounding legislative districts. Inability of a metropolitan-wide entity to raise funds and determine policy and investment strategies for the entire 'functional' area inevitably results in dysfunctional transportation, infrastructure, housing, and environmental policies that cannot be solved within the confines of limited political boundaries.