FIBONACCI : a leading indicator This name refers to a set of mathematical and graphical considerations, based on the eponymous series. This latter, formalised by the famous 13th century Italian mathematician, is expressed as: the sum of the two preceding terms (i.e. Un+2 = Un+1 + Un), with the first two terms being 1 and 1 (i.e. U0 = U1 = 1). The first terms of the series are thus: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, … This series has very numerous interesting properties, the most useful being the limit of two consecutive terms of this series. Indeed, the Un+1/Un ratio aims at the golden ratio (about 0.618) for n infinitely high. In the field of finance, this ratio and its fractions are used to determine resistance and support levels as well as targets. The main proportions used are 38.2 %, 50 % and 61.8 %. They are used to determine what is called “retracements”. Let us take the example of a stock, which following the announcement of good news or a speculation wave, rises from 100 (the