Engine of enterprise in the push and pull of rural desertion
Today, about 180,000 people around the world will leave the countryside and move to a city. Humans are becoming urban creatures at an accelerating speed. The United Nations calculates that London's population took 130 years to grow from 1m to 8m. Bangkok in Thailand took 45 years, Dhaka in Bangladesh 37 and Seoul in South Korea just 25.
Cities are the future. Whether they turn out to resemble the gleaming perfection promised by the Emerald City in the Land of Oz or the dystopian chaos ofBlade Runnerwill depend on the technology and governance of future economic development.
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For centuries the move towards a concentration of people in towns was driven by an unrelenting logic of progress. Crudely put, the profits needed to drive industrialisation came from greater productivity in agriculture. More productive agriculture almost always meant bigger farms and fewer on the land. Factories required workforces both large and close, which generally meant towns and cities. Trade between them in turn increased demand for transport hubs. Thus were rural economies urbanised.
Much of the world, especially China and India, is still going through this process, with a time-scale telescoped by the pre-existence of mass production technology. But that does not mean cities develop in a predestined fashion. For the growing number of modern cities that long ago left behind the industrial reasons for their existence, modern technology, globalisation and policy create subtle forces that can shape, create or undermine them.
The effect of government policy on cities can make a dramatic, and damaging, difference, as much when they are favoured as when they are not. A striking example is the "copper belt" of Zambia, where the country's longest-established export is mined. Kenneth Kaunda, Zambia's first president after independence, calamitously used tax revenue from the soaring price of copper to fund urban food subsidies and other hand-outs, in effect taxing the countryside to favour the towns. A mass rural decampment ensued. Ndola, the copper belt's biggest centre, is today a neat colonial-era company town of copper miners surrounded by shanty towns of more than 1.5m desperately poor Zambians trying to live off them.
The lessons of history are clear: cities do better if they prepare for migrants. And it is easier to deal with people "pulled" towards cities by the prospect of jobs and better lives than those "pushed" by eviction from the countryside.
The British Isles contain three models of the move from rural to urban. As in England, it can be gradual and relatively painless: the "enclosure" by landowners of small tenant farms and publicly held land into bigger enterprises took centuries and monarchs in the 16th and 17th centuries tried to slow the process down to placate protesting villagers. Later, country-dwellers often voluntarily moved to towns when industrialisation created better jobs, in textile mills and the like. As in Scotland, the move can be brutal and abrupt, such as the Lowland and Highland Clearances - the forced removal of tenant farmers to make way for bigger and more productive farms - that began in the 18th century. Glasgow and Edinburgh were inundated with indigent refugees. And as in Ireland, the change can be achieved in a way that in practice if not intent resembled genocide - the famine and land evictions of the mid-19th century that helped to populate Liverpool, Boston and New York.
Thus cities such as Shanghai, to which millions of rural Chinese are desperate to move but are regulated by internal migration controls, do rather better than Mumbai, where refugees fleeing drought and crop failure in the villages of India mean that more than half the city's population live in shanty towns or slums.
Important though government is, it operates in a landscape shaped by technology and globalisation. Just as the growth of cities was driven by one technological revolution, so others can change or reverse it. Edward Glaeser, a Harvard specialist in the economics of cities, points out that the original reasons for the existence of cities are disappearing. The cost of transporting manufactured goods dropped by 90 per cent in real terms in the 20th century, removing the need for regions to have their own manufacturing and distribution hub.
"The great force that reshaped the city in the 20th century is the engine," Prof Glaeser says. "People have increasingly been able to propel themselves and their goods over long distances."
Cheap transport pushed Americans away from Cleveland and Detroit and towards the cheap land and warm weather in sprawling low-density sunbelt cities such as Phoenix, Arizona. Liverpool, the port in north-west England that handled much of Britain's transatlantic trade, was once the country's richest city. The decline of its port almost halved its population from 867,000 in 1937 to 442,000 in 2001.
The revolution of information technology and digitisation ought, perhaps, to have completed the job, removing the need for a physical workplace. Yet several of the cities that seemed to be dying in the 1970s - New York, Chicago, Boston and London - have since had remarkable revivals. Even those, such as New York, whose populations are still stagnant have experienced booming property markets and the reclamation of derelict districts.
The success of the modern city appears to have two features: one, that digitisation has created a very specialised elite who benefit even more from clustering together and, two, that people are moving to cities not just to work but to play. The industries that are most digitised and computerised - software and financial services - are those that huddle in small, expensive areas such as Silicon Valley and Wall Street, where their top-level staff still need the edge of face-to-face contact with clients and with each other.
Saskia Sassen, a sociologist at the University of Chicago, notes that Goldman Sachs has removed a lot of standardised work, including basic trading, to cheaper locations such as New Jersey - but is building a global headquarters, including six trading floors, in lower Manhattan. "An industry like finance uses new technologies but is not about them," she says.
Meanwhile, Prof Glaeser notes that the ratio of housing costs to real wages in cities has risen sharply, suggesting that people are choosing to live in cities for reasons other than income. With falling crime rates, the attractions of some cities - bars, restaurants, theatre, not to mention the city as a marriage market - have launched their renaissance as a place of consumption.
Some cities achieve this transformation; some do not. Now that Great Lakes shipping is no longer a big industry, there is no reason to site trading and manufacturing cities on the lake shores. But while one, Detroit, has largely failed to find a new role, another, Chicago, has thrived.
Managing the post-industrialisation of a city looks to be even harder than managing its urbanisation. Some, like the southern Indian information technology city of Hyderabad, have to do the two simultaneously. The Blade Runner and Emerald cities may end up co-existing. Not all urbanisations will look the same.
人类是怎么成为城市动物的？
今
天，全世界将有大约18万人离开农村迁往城市。人类正以越来越快的速度变成城市动物。根据联合国的计算，伦敦的人口从100万增加至800万，用了130年的时间，泰国的曼谷以及孟加拉国的达卡分别用了45年和37年，而韩国的首尔仅用了25年。
城市代表着未来。至于它们是像奥兹国(Land of Oz)中的翡翠城(Emerald City)所呈现的那样完美亮丽，还是像《银翼杀手》(Blade Runner)中那种可怕的混乱，将取决于科技以及人们对未来经济发展的管治。
<p>几百年来，一种无情的发展逻辑，推动着人口向城市集中。可以说，推动工业化进程所需的利润，来自于农业生产率的提高。更为高产的农业，几乎总是意味着农场规模的扩大和农业人口的减少。工厂需要大量并且住在附近的劳动力，这往往意味着城镇和都市。而城镇之间的贸易，又推动了对运输中心的需求。农村经济就这样被城市化了。
中国印度仍在经历城市化过程
世界上的许多地区，特别是中国和印度，仍在经历着上述过程，而已经存在的大规模生产技术，缩短了这个过程所需的时间。然而，这并不意味着城市在按照预先设定的模式发展。对于越来越多在工业层面早已失去存在理由的现代城市而言，现代科技、全球化以及政策产生了微妙的力量，这些力量可以起到塑造、创建或者破坏城市的作用。
政府的城市政策，可以造成戏剧性、破坏性的效果，而不论这些政策的本意是否是要让城市得益。一个显著的例子，就是赞比亚的“铜带”(copper belt)地区，铜是该国历史最为悠久的出口产品。赞比亚独立后的第一任总统肯尼思?卡翁达(Kenneth Kaunda)灾难性地将铜价飙升所带来的税收收入，用于城市地区的食品及其它补贴，这实际上向农村征税来补贴城市。随之而来的，是农村人口大量迁走。而今，铜带最大的中心恩多拉，是一个不折不扣的殖民风格铜矿公司城，周围全是贫民窟，超过150万极度贫困的赞比亚人在此谋生。
历史的教训非常清楚：如果城市对移民有所准备，将做得更好。而且，对付那些被城市工作的前景和更美好的生活“吸引”出来的人们，比那些被从农村里“推”出来的人要容易。
英伦三岛包含三种从农村迁移至城市的模式。在英格兰，这种迁移是渐进的，而且相对不那么痛苦：小型租赁农场的所有者们的“圈地”和将公有土地变为更大企业的过程，花费了数百年的时间，而16世纪及17世纪的君主们曾努力减缓这一过程，以安抚抗议的村民。后来，当工业化在纺织及其它行业创造出更好的就业机会时，农村人口往往自发地迁至城镇。而在苏格兰，这种迁移经常是野蛮而突然的，如始于18世纪的苏格兰低地和高地清除――强迫佃农迁走，为规模更大、产量更高的农场让路。格拉斯哥和爱丁堡被贫困的难民所淹没。在爱尔兰，从农村向城市的迁移，实际上不啻为一次有计划的屠杀，即便并非有意为之 ―― 19世纪中叶发生的饥荒和土地掠夺，给利物浦、波士顿和纽约带来了大批移民。
上海等城市比孟买做得要好一些。因干旱和粮食歉收从印度农村逃出的难民，意味着孟买一半以上的人口居住在贫民窟。数以百万计的中国农民也拼命想迁往上海，但他们受到中国对国内人口流动的限制。
尽管政府的作用很重要，但城市化进程却是在科技和全球化塑造的背景下进行的。正如城市的发展是由某一次科技革命来推动的，其它科技革命也可以改变或逆转这一过程。哈佛大学(Harvard)城市经济学专家爱德华?格莱泽(Edward Glaeser)指出，城市存在的初始理由正在消失。20世纪，制成品的实际运输成本下降90%，使得各地区不再需要建立自己的制造及配送中心。
内燃机：20世纪重塑城市的主要推动因素
“20世纪时，重塑城市的主要推动因素是内燃机，”格莱泽教授表示。“人们越来越有能力将自己和货物运送到很远的地方。”
廉价的运输成本促使美国人离开克利夫兰和底特律，迁往土地便宜、气候温暖、人口密度极低的“阳光带”城市，如亚利桑那州的菲尼克斯。英格兰西北部港口城市利物浦处理着英国的许多跨大西洋贸易，它曾经是英国最富裕的城市。该市港口的衰落，几乎使其人口减半，从1937年的86.7万人降至2001年的44.2万人。
信息技术和数字化革命或许应当完成这一任务，使人们不再需要有形的工作场所。不过，在上世纪70年代似乎“奄奄一息的”几个城市――纽约、芝加哥、波士顿和伦敦――自那以后出现了值得称道的复苏。连纽约那些人口增长仍停滞不前的城市，也经历了房地产市场的繁荣，以及对旧城区的改造。
数字化精英更需要聚居
现代城市的成功似乎包含两个特点：其一，数字化缔造了一个非常专业化的精英群体，他们从聚居得到的益处更多；其二，人们迁往城市的目的不仅是工作，还有娱乐。最数字化和计算机化的产业（如软件业和金融服务业），往往挤在面积不大但价格昂贵的地区，例如硅谷和华尔街，它们的高层员工仍然需要与客户和同僚面对面交流的优势。
芝加哥大学(University of Chicago)社会学家萨斯基亚?扎森(Saskia Sassen)指出，高盛(Goldman Sachs)已将基本交易业务等大量标准化工作，转移至新泽西州等成本更为低廉的地方，但该公司却在曼哈顿下城区建造一个全球总部大楼，内有6个交易大厅。她表示：“金融这样的行业使用新科技，但并非仅此而已。”
城市的魅力
与此同时，格莱泽教授指出，城市住房成本与实际工资的比率已大幅提高，这表明人们选择居住在城市，是出于收入之外的其它原因。随着犯罪率的不断下降，一些城市具有吸引力的地方――酒吧、餐馆、剧院，更遑论城市作为婚姻市场的角色――带来了它们作为消费场所的复兴。
有些城市实现了这种转型，另一些城市则未能实现。既然北美五大湖的航运已不再是一个大型产业，那就没有理由将贸易和制造业城市放在五大湖畔。不过，尽管其中一个城市底特律基本上未能找到自己的新角色，但另一个城市芝加哥已在繁荣发展。
与管理一个城市的城市化进程相比，管理其后工业化时期似乎更为困难。像印度南部信息技术城市海得拉巴等一些城市，则不得不同时进行上述两项工作。《银翼杀手》中乌烟瘴气的城市与“翡翠城”那样近乎完美的城市最终可能并存。并非所有的城市化进程都是相同的。
