Beware of extrapolation, a former British chancellor of the exchequer once remarked: it can make you go blind. The warning should be heeded by those western observers who, dazzled by China's rise in basic manufacturing, breathlessly proclaim it is destined to become a global leader in science and technological innovation.

Such predictions are invariably based on now familiar statistics and trends: the millions of graduates churned out by China's universities, the rapid growth of its research and development spending and its increasing output of patent filings and scientific papers.