This paper analyzes two great traditions in the measurement of the economic cycle: the cyclical indicators and the calculation of aggregate non-observed variables such as potential product, natural interest rate, natural unemployment rate and equilibrium exchange rate, and their associated gaps. The first tradition, also known as the empirical vision of the cycle, owes much to the effort of the nber and developed considerably, especially in the advanced economies. In Colombia, a lot of work has been done in that direction. However, few of these survive, resulting in the country losing a valuable instrument in the analysis of the economic conjuncture. This document is the first part of the complete work and tells the story of the first tradition.