As historians have extended the scope of their work, they have also equipped themselves with new methods and tools, the better to practice their craft. No longer do historians merely pore over the same old chronicles and documents to ask whether Charles the Fat was at Ingelheim or Lustnau on July 1887. To introduce the evidence of statistics, they learn the methods of the computer scientist. 23 , they study economics. 24 , they become archeologists, studying fossil remains, fragments of pots, or modern city landscapes. 25 , they draw on the insights of social psychologists and cultural anthropologists. To deduce marriage patterns or evaluate the effect upon an entire population of wars and plagues, they master the skills of the demographer.