April 2002 Composite Leading Indicator - - Methodological Notes The OECD CLI is designed to provide early signals of turning points (peaks and troughs) between expansions and slowdowns of economic activity. The OECD uses the six-month rate of change of the CLI as its preferred pointer to possible turning points. The six-month rate of change of the CLI is calculated by using the ratio between the figure for a given month m and the average of the figures from m-12 to m-1. Thus, the six-month rate of change is less volatile and provides earlier and clearer signals for future turning points than the CLI itself. In practice, peaks in GDP have been found about nine months (on average) after the signals of peaks had been detected in the six-month rate of change. The OECD has compiled CLIs, which summarise information contained in a number of key short-term economic indicators known to be linked to GDP, for 22 member countries since the 1980s. The CLI is an instrument of analysis that has to be used carefully. The OECD CLI is designed to provide qualitative information on short-term economic movements rather than quantitative measures. Therefore, the main message of CLI movements over time is the increase or decrease. The CLIs are aggregated time series, and have been compiled using a modified version of the method developed by the US National Bureau of Economic Research. In general, the index of industrial production covering all industry sectors (IIP) is used as a proxy measure (or reference series) for GDP as historical turning points of IIP have coincided with those of the entire economies for most OECD countries. The CLI comprises a set of component series selected from a wide range of key short-term economic indicators (170 in total, about 5-10 for each country). The component series selected are those known to provide an indication of future economic activity. They will also be suitable when changes in economic structures occur in future.