  Statisticians in the first part of the 19th century were concerned with the collection of data, but not with analysis. The data suggested too many different causes. Statistical journals published tables and numbers, but graphical representations and analysis remained absent. In 1863 Jevons published A Serious Fall in the Value of Gold, which investigated the influence of Australian and Californian gold discoveries of 1851 on the value of gold. For this purpose he constructed index numbers making use of the geometric mean. He argued that multiplicative disturbances will be balanced off against each other when using the geometric mean. There is however no empirical verification of this ‘multiplicative disturbances’ hypothesis. Aldrich (1987) argues that Jevons used probability in two main patterns of argument: in the determination whether events result from certain causes or are rather coincidences, and in the method of the least squares. The first approach entails the application of the ‘inverse method’ in induction: if many observations suggest regularity, then it becomes highly improbable that these result from mere coincidence.   The second approach, the method of the least squares, appears when Jevons tries to adjudge weights to commodities (giving more weight to commodities that are less vulnerable to price fluctuations), and when he tries to fit empirical laws starting from an a priori reasoning about the form of the equation. These methods show at least some concern for probability and the theory of errors.   But Jevons worked on the limits of his mathematical understanding, and many ideas that he foreshadowed were not developed until decades after his death.