Sir

Scientists teach students to evaluate critically the significance of their measurements, and to eschew meaningless decimal places thrown up when pocket calculators work out a quotient of two integers. So what are we to make of the recently released impact factors, including Nature's much advertised rating of '31.434' (see also http://www.nature.com/nature/about)? Has Thomson Reuters discovered a protocol that allows it to measure the impact of a journal with an accuracy of 32 p.p.m.?

Quoting this figure conveys the wrong impression — that innumerate marketing is trumping common sense at the heart of science's leading journal.