 Expansion or redevelopment is not really a choice. As cities grow in population and income, they both expand and densify. They grow both outwards, inwards and upwards. There's a lot of metropolitan outward expansion taking place and it is usually underestimated. The Paris Metropolis, for example, grew by 250 times between 1800 and 2015. And the rates of urban expansion are typically faster than the rate of population growth. We've heard that before. Between 1800 and 2015, the population of Paris grew by only 22 times. Its area grew by 250 times. Before I continue, I want to make a comment about what Mark said just now. And what I think is happening is that there is a race, a race between expansion and densification. We've been talking about densification for 30, 40 years and we've made very little progress. And we are in the midst of what I call the urbanization project. The movement of people into cities. That project started around 1800. Before that, there were always less than 10% people living in cities and there was no urbanization. People started to urbanize in 1800. By now, there are half the people are living in cities. By the end of the century, two thirds to 70% will live in cities and the urbanization project, the movement of people from the rural areas to cities will come to an end. We have now a window of opportunity to intervene in the shape of cities. And the discussion here is whether we are going to intervene in time to make these cities more productive, more inclusive and more sustainable. The rates of urban expansion as we've studied in these sample of cities that Dr. Claus was talking about are not only in sprawling American cities, they are true of less developed countries as well. The population of less developed countries to take a more recent example doubled between 1990 and 2015, while their overall urban extent increased by three and a half times. Most mayors don't understand that. That cities increase in area three and a half times in 25 years. The reason densities are in decline. History, in other words, is not on the side of the compact city agenda. On the contrary, average densities have been in a long term declined from their peaks in many countries for a century or more. We measured densities in a sample of 200 cities described by Dr. Claus. In less developed countries, they declined at the rate of 2.1% per year. In more developed countries, they declined by one and a half percent per year. The urban extent of cities is simply a function of their population and their income. The population of cities and their income together explained 85% of the variation of urban extent among cities. Here you see an example. The Lagos on the left, Paris on the right, same population. The GDP of Paris is 10 times that of Lagos. The area of Paris is three and a half times that of Lagos. Why? Because as people become richer, they consume more of everything. In particular, they consume more housing and therefore more land. We do not expect a family that quadruples its income to move to a smaller apartment, no matter how many coffee shops there are in the neighborhood. Population and income growth drive outward urban expansion hand-in-hand with a selective redevelopment of established neighborhoods. What you see here is Shenzhen expanding sideways and upwards at the same time. The problem we now face and in many places it has now taken the dimension of a crisis described by Dr. Claus is that most policymakers, including most urban planners, are in denial about the two dimensions of urban expansion. Many of those who are in denial are those who decry urban expansion as sprawl, a bad word, and want to stop it to contain it to arrest it. They preach defensive urbanism wanting to protect and save their cities from sprawl. I worry about that. I'm a housing person. I dedicated my professional career to do something about the housing problem, especially in the housing problem in the cities of the developing countries. I've come to one important conclusion over the years. The housing problem is basically a land problem. If poor people can obtain a plot of land close enough to job opportunities, they can gradually house themselves over time. They cannot house themselves in apartments because apartments require finance and poor people don't have access to finance. This has convinced me that to make cities more inclusive, we must keep residential land in ample supply. And we can only do so on the urban fringe by preparing adequate lands for building and making these lands accessible to job markets. I'm therefore against defensive urban policies, against policies that preach containment and that want to limit urban expansion. These policies are anathema to affordable housing and therefore to inclusive cities. In all cities where containment has been successful, housing has become unaffordable to all but the very few. London and Seoul, with their famous green belt, brought it upon themselves. Chinese cities that are preaching food security and the preservation of cultivated lands in and around cities have gotten the same result. The compact city agenda, when it succeeds, compromises affordable housing. It empowers sitting residents under the guise of an environmental agenda to protect their property values by keeping newcomers out. The compact city agenda creates a different kind of damage when it fails. Our recent global survey shows that the majority of cities have now adopted one or another containment strategy, be it a green belt or an urban growth boundary. These strategies do not appear to slow down the rate of expansion but they definitely discourage municipal authorities and city planners from anticipating urban expansion correctly and preparing for it. Indeed, why make plans to accommodate something that you find unacceptable? Worse yet, won't making such plans accelerate urban expansion, making cities sprawl even more? This, I'm afraid, is a ridiculous position, especially now that we cannot prevent people from moving to cities. It is much like saying that you don't want your city to flourish because it will become more attractive and more inviting to people, failing to anticipate urban expansion and to prepare for it, especially by laying out the urban periphery before development occurs, does not prevent urban expansion. It simply produces, as Dr. Kloss has demonstrated, disorderly urban expansion that makes the city less productive, less inclusive and less sustainable. Our research shows that areas of expansion in cities the world over, areas that were developed between 1990 and 2005, are more disorderly than areas developed before 1990. Planners are simply not doing their job. Largest cities are generally more productive than smaller ones. I have to skip. I have to go faster. This is what happens when we don't have proper preparation, an area of Bangkok with eight kilometers between its arterial roads. This is Toronto, the public transport system that runs when you have arterial roads. And this is our, these are our programs to get cities in Ethiopia and in Colombia to plan for their expansion. Making room for urban expansion can make for more inclusive cities, for more productive cities and for more environmentally sustainable cities. Surely, we must encourage cities to densify. We need urgent regulatory reforms that allow for smaller apartments, higher buildings, more plot coverage, a larger share of the land in residential use and greater saturation of urban urban space. But these interventions are more costly. They take more time. And last, but not least, they are resisted by sitting residents because they change the character of neighborhoods. For now, making room for urban expansion is the only realistic strategy accommodating the growing population of developing country cities where virtually all urban population growth in the coming decades will take place. Thank you.