When I was a child growing up in England three decades ago, I was confronted with the visual evidence of social mobility every day– but of the downward, not upward, type. 30年前，当我还是个孩子的时候，我住在英格兰，每天都目睹表明社会流动性的“视觉”证据，不过流动方向是向下的，而不是向上的。
We lived in a suburban, middle-class home. On the walls, however, hung the portrait of an 18 th-century Anglo-French aristocrat, a maternal ancestor. In the intervening centuries, my aristocratic forebears had lost their status and wealth due to drink, gambling and poor decisions. Thus, my only link with royalty was that portrait and the fact that I have the same unusual middle name– Romaine– as the noblewoman in the picture. 我们是生活在郊区的中产阶级之家。但家里的墙上挂着一幅 18世纪英法贵族的画像，她是我母亲家族的一位祖先。从她往后的几个世纪里，我的贵族祖先们由于饮酒、赌博和一些糟糕的决定而失去了地位和财富。因此，我与贵族仅有的联系就是那幅画像，以及我有一个不同寻常的中间名罗曼 (Romaine)，与画像中的贵妇一样。
A rare example of social mobility or a widespread pattern? Today, that is a very politically charged question, particularly in countries such as the US. But it is also a very hard question to answer definitively. 这是社会流动性的一个罕见例子，还是一种普遍模式？如今，这是一个充满政治意味的问题，尤其是在像美国这样的国家。但这个问题很难明确回答。
Social mobility is an issue about which politicians love to pontificate but about which we actually know surprisingly little. Economists have generally tracked mobility by looking at surveys on wealth, jobs and educational attainment over two or three generations. This has typically shown that mobility is highest in the Scandinavian countries and lowest in places such as Latin America, with the US and UK lying halfway in between. 社会流动性是政治人士喜欢夸夸其谈的一个问题，但实际上我们对它的了解出奇地少。经济学家一般通过考察两、三代人的财富、就业和教育程度来追踪社会流动性。这些研究一般表明，斯堪的纳维亚国家的社会流动性最高，拉美等国最低，美国和英国介于二者之间。
Interestingly, these surveys tend to show that more mobile societies such as Sweden are also more equal, as determined by the Gini coefficient, the most commonly used measure of inequality, and vice versa. The idea that you can justify high levels of inequality in some nations because there is plenty of mobility– as US politicians are apt to do– does not ring entirely true, based on the economic numbers. 有趣的是，这些调查往往表明，瑞典等社会流动性较大的国家也更为平等，与基尼系数（ Gini coefficient，最为常见的衡量不平等程度的指标）所显示的一样，反之亦然。有人认为，可以把一些国家的高度不平等说成合理的，因为它们的社会流动性很大——美国政客就经常这么说。但根据经济数据，这种看法并不完全正确。
The problem with this widely cited economic data are that they are very limited: it typically only tracks families over a generation or two and cannot capture subtle social patterns. So Gregory Clark, an economic historian at the University of California, Davis, has recently attempted to use another innovative approach that blends sociology, economics and history. In a new book, The Son Also Rises, he has analysed surnames in historical databases around the world to work out how families have risen in terms of wealth and status over multiple generations. In the US he looked at doctors; in the UK, at elite universities such as Oxford and Cambridge; and in Sweden, land records. 这些被普遍引用的经济数据的问题在于，它们非常有限：它们对家族数据的追踪通常仅限于一、两代人，无法捕捉微妙的社会模式。因此，美国加州大学戴维斯分校( University of California, Davis)经济历史学家格里高利•克拉克( Gregory Clark)最近尝试运用另一种创新方法，把社会学、经济学和历史学结合在一起。在其新书《虎子崛起》( The Son Also Rises)中，他对全球历史数据库中的姓氏进行了分析，考察家族财富和地位是如何在好几代人时间内上升的。在美国，他考察了医生；在英国，他考察的是牛津 (Oxford)和剑桥 (Cambridge)等精英大学；在瑞典，他考察的是土地记录。
This approach– like the econometric one– has its limits. Historical lists of surnames or elite jobs can be patchy, particularly since they are dominated by the paternal line. ( My story of maternal downward mobility, for example, would have been missed.) But Clark reaches some thought-provoking conclusions. First, he argues that if you look at multiple generations, social mobility is lower than widely presumed in most nations. Second, there is less difference between nations than usually thought. Those“ egalitarian” Swedes are not as mobile as presumed. But in America, Clark rejects the idea that mobility has recently declined sharply as social polarisation has grown– an idea posited, for example, in Coming Apart, an influential book published last year by the political scientist Charles Murray. Clark argues that mobility is indeed low in America but insists it has always been thus. 这种方法（类似计量经济学方法）有其局限性。姓氏或精英职业的历史清单可能是不完整的，尤其它们主要是父系数据。（例如，我母亲家族的向下流动会被遗漏。）但克拉克得出了一些发人深省的结论。首先，他主张，如果从好几代人的数据来看，多数国家的社会流动性低于人们普遍的想象。其次，国家间的差异小于人们通常的想象。“主张平等”的瑞典人的社会流动性并不像人们想象的那样大。但对美国，克拉克并不同意以下观点：由于社会两级分化现象加剧，社会流动性最近大幅下降——这是政治学家查尔斯•默里( Charles Murray)去年出版的颇具影响力的著作《分化》( Coming Apart)中的看法。克拉克指出，美国的社会流动性确实很低，但他坚持称，该国一直如此。
