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¿Media o mediana? ¿Cuál estimador usar? Caso de la expectativa de inflación a 12 meses
Collado-Chaves, Andrea
The main purpose of this technical note is to guide users of the Monthly Survey of Inflation Expectations and Exchange Rate, conducted by the Central Bank of Costa Rica, in selecting the mean and median of the inflation expectations when both estimators are different. The time series of the mean and median since January 2006 to December 2019 were used to prove that, in average, the mean is statistically greater than the median. The positive outlier are in part responsible for this gap. These values appeared when the sample size was enlarged and the participation of entrepreneurs in the Survey was increased. They tend to decrease after December 2014 when 95% of the samples was replaced. In order to eliminate the outliers, two series were calculated: one without outliers and one without extreme observations. The results indicate that the four series: mean, mean without outliers, mean without extremes and median have bivariate correlation close to 1, therefore they measure the same expectations. When users must select only one estimator for a specific month, it is recommended to use the median if the mean is greater by 0.1 percentage points (p.p.) or more. If the time series is required, it is suggested to compare the results using the mean and median, and evaluate which one is better according to the research goals.
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