In the late 18th century, Johann Gottlieb Beckmann, a Saxon forester, hit upon the idea of systematically surveying Saxony's forests. He dispatched trained surveyors into a tract of woodland to hammer nails into every tree. Each man carried nails of five different colours, enabling them to grade trees by size. When every tree was marked and the men emerged, Beckmann counted the coloured nails left over to calculate the exploitable resources.
Efforts to measure what goes on in the economy have a chequered history. The political scientist James C. Scott, who unearthed the example of Beckmann, points out that forest planners tried to conform to Beckmann's theories, spacing with architectural precision trees of the same breed and age. The resulting forests were vulnerable to high winds and to disease.
Sir William Petty, an adviser to Oliver Cromwell, produced the first estimate of Britain's national income, which he put at £40m a year back in 1664. But Petty's surveys also made it easier for the English to exploit Ireland. William the First's Domesday book is both a historical treasure and the tool of a conqueror.
