In last week's Economist, the Free Exchange column explored the issue of social mobility across generations. In other words, how much are differences in income in one generation attributable to the previous generation and earlier generations? In other words, how much of the income of the readers of this blog is determined by the income of their parents, grandparents etc.? Greg Clark and Neil Cummins have used rare surnames to measure social mobility rates over the long run (i.e., 200 years plus). They find that social mobility is low in the long run as 70-80% of economic advantage appears to be transmitted from one generation to the next. Click here for an overview of this fascinating research. However, the ultimate question is how much of this economic advantage is down to nature and how much is down to nurture?
The Berkeley Earth Project , an independent study of global warming, has found that the earth has become a degree warmer over the past half century. However, the statistical uncertainty surrounding pre-1920 estimates makes it very hard to say much about long-term trends - click here for graph . This is one of my concerns with the global warming debate - we simply don't have trustworthy long-run data which looks at temperature changes over the last millennium (or two). My second concern with the global warming debate is that it is very hard to prove any sort of casual link between global warming and human activity. The scientists may be able to show correlation between global warming and our production of carbon dioxides etc., but correlation is not causation. My third concern with the debate is that those who are sceptical or agnostic are stereotyped as flat-earthers or intellectually-challenged crackpots. This only stifles debate and the progress of science itself.