This document estimates the bias in the inflation measured through the CPI. The methodology used was to find Engel curves, that is, a demand was estimated for the share of food expenditure based on the real expenditure of households, where, in addition, a group of controls associated with the sociodemographic characteristics of each household was included in 23 metropolitan areas. The data used correspond to the Survey of Income and Expenses for the years 1994/95 and 2006/07, where there were 11260 observations. The results show an average annual overestimation of inflation of 1.61 percentage points, consistent with the results of previous authors. Similarly, calculations of elasticities of expenditure (0,51) and price (compensated (0,19) and not compensated (0,35)) were included, finding that food are normal-basic and inelastic goods, as it is posed by the economic theory.