Orchid, Venice, Paris, etc., are important commercial and trade centers; Venice was in its heyday, with a population of more than 200,000. After the industrial revolution, the process of urbanization was greatly accelerated, and as farmers kept coming to new industrial centers, the city had achieved unprecedented development. By the eve of world war I, most of the population of Britain, the United States, Germany, France and so on had already lived in cities. This is not only a sign of abundance, but also a symbol of civilization.
Sensible producers and operators certainly do not produce goods that no one needs. Choose to produce goods that someone has bought. The problem, however, is that the demand for certain goods is constantly changing. There are a number of factors that affect the needs of potential customers. For example, the increase of residents' income will gradually reduce the consumption of low-grade and outdated goods, and then shift purchasing power to higher-level, novel products. A kind of high commodity prices is a lot of people think that spending it uneconomical and seldom buy it, but when its price falls, people will have the idea of consumption value, is willing to buy more, and spend more. Potential customers' desire for a commodity is never stable. The change of purchasing desire must affect the payment direction of purchasing power, resulting in the change of market demand. For such a change, producers and operators may lack information, and thus are in a passive state after the change.
The residential floors are divided into low-rise residences (1-3 floors), multi-storey residences (4-6 floors), mid-level residences (7-9 floors), high-rise residential buildings (10 floors and above), public buildings and comprehensive buildings; The total height is more than 24 meters high, but it does not include single-story buildings that are more than 24 meters high; Buildings with a total height of more than 100 meters, both residential and public buildings, are known as supertall buildings.