What are the benefits and costs of a diverse population? How should a liberal democracy define the limits of multiculturalism? In answering these questions, the high-income countries will also define what kind of society they wish to be in the 21st century.
人口多元化的好处和代价分别是什么？一个自由的民主国家应怎样界定多元文化主义的界限？通过回答这些问题，高收入国家也就明确了，它们希望在 21 世纪成为怎样的社会。

As the World Bank's latest Economic Prospects report makes clear, the pressure for migration from poor to rich countries is a permanent feature of our integrating world. The share of migrants in the populations of the high-income countries rose from 4.4 per cent in 1960 to 11.4 per cent in 2005. It seems certain to rise still further, given both demographic trends and the persistent gaps in incomes and wages between developing and high-income countries.
正如世界银行(World Bank)最新的《全球经济展望》(Global Economic Prospects)报告所阐述的那样，在世界日趋一体化的过程中，从穷国向富国移民的压力将是一种长期存在的特征*。在高收入国家中，移民占全部人口的比例已从 1960 年的 4.4%，上升至2005 年的 11.4%。鉴于目前的人口趋势，以及发展中国家和高收入国家间持续存在的收入差距，这一比例似乎将必然继续上升。

A vigorous and often ill-tempered debate has opened over the consequences of this movement of people. In a thought-provoking new book, Philippe Legrain, the British author of Open World, a splendid work on globalisation, takes a bold position: let them all in. More precisely he says: It would be best if our borders were completely open. But if that is deemed impossible for now, let them at least be more open. And if even that is not acceptable, let them at least be better regulated.
围绕着移民产生的后果，一场言辞激烈且通常争到面红耳赤的辩论已经展开。在发人深省的新书《开放世界》(Open World，一部探讨全球化问题的优秀著作)中，其英国作者菲利浦•勒格兰 (Philippe Legrain)提出了一个大胆的观点：让他们全都进来**。更确切地讲，他在书中表示：我们最好完全开放边境。但如果有关当局认为这在现阶段是不可能的，那么至少应该提高边境的开放程度。如果连这也无法接受，那至少应该改善边境的监管。

Mr Legrain performs an invaluable service: he makes a good case for the unpopular cause of free flows of people. The book is a superb combination of direct reportage with detailed analysis of the evidence.
勒格兰做出了一项宝贵的贡献：他为缺乏认同的人口自由流动原因，提供了有力的论据。这本书出色地将直接报道和对证据的详细分析结合在一起。

What I find missing, however, is analysis of what might happen if no restrictions were indeed placed on the movement of people. Basic theory suggests that the flow of migrants to a place where there is a chance of obtaining a far better income might continue until the wages to which the migrants aspire have fallen to the same level as at home (after adjustment for the costs both of moving and of living). Alternatively, it would continue until the condition of many of them has become even worse than at home. We would then see in the developed world what we see in developing countries: vast slums.
但我发现，对于完全取消移民限制所可能产生的后果，书中未作分析。基本理论表明，只要人们有机会在某国获得比本国高得多的收入，就会发生移民，直至他们的预期工资与本国收入持平为止（在考虑迁移和生活成本后）。换言之，这种人口流动将持续到他们之中许多人的境况变得甚至比在国内更糟糕为止。那时，我们就将在发达国家看到发展中国家中常见的景象：大量的贫民窟。

No high-income country is going to allow this to happen. For this reason some controls will remain in place. Moreover, such controls are effective, even if porous. The gaps in wages across the globe to which Mr Legrain points in arguing the economic benefits of free flows also demonstrate the efficacy of controls. Making migration both costly and unpleasant works. But those costs are indeed enormous, as is always the case when market forces are driven underground.
任何高收入国家都不会允许这种局面出现。出于这一原因，一些限制措施将继续存在。此外，尽管这些措施漏洞重重，但却仍然有效。勒格兰在阐述人口自由流动的经济益处时，提到了全球范围内的工资差距，这种差距也恰恰证明了移民控制措施的效果。让移民变得成本高昂而且不那么愉快的措施发挥了作用。但实际上，这些成本的确很高，因为当市场力量被地下力量所取代时，情况往往如此。