Use of informal mobile telephony in low income households in Colombia

Access to mobile telephony in Colombia exhibits rather interesting features compared to other countries. Colombia witnessed the beginning of a new alternative for communication consisting in the use of informal resale of minutes on the streets and small stores during the first years of this century. In this paper we are interested in analyzing the main factors that determine the utilization of this kind of service. We use a probabilistic model to explain the characteristics of the people that use `informal resale´ on the streets and we find that people in the modality of prepayment and people from small cities has a higher probability of using this alternative. It is also found that people in the firm-leader use more often this service. These results seem indicate that price differentials among on-net and off-net and between prepaid and postpaid are the causes of the rise of this economic activity.***El acceso a la telefonía móvil en Colombia evidencia ciertas particularidades con respecto a otros países. En Colombia surgió una nueva alternativa de comunicación que consistía en la venta de minutos de celular en las calles y en pequeños negocios durante los primeros años de ésta década. En este documento se analizan las principales características de quienes usan esta modalidad de comunicación con base en una encuesta dirigida a usuarios y no usuarios de bajos ingresos. Se usa un modelo probabilístico para explicar las características de las personas que lo usan y se encuentra que las personas que están en la modalidad de contrato prepago y que viven en ciudades pequeñas tienen una mayor probabilidad de usar esta alternativa de comunicación. De otro lado se encuentra que quienes están con el operador dominante tienden a usar este servicio también de una forma más notoria. Estos resultados parecen indicar que los diferenciales de precios entre las llamadas off-net y on-net así como entre prepago y postpago son los que alimentaron el surgimiento de esta actividad.Mobile telephony, ICT, gender gap, Resale

An approximation to the digital divide among low income people in Colombia, Mexico and Perú: two composite indexes

This study examines the determinants of information and communications technology(ICT) use and access of low-income people in three developing countries: Colombia,Mexico and Peru. We focus on cross-country differences and similarities in ICTs use acrossgender, age, education and income, using two composite indicators of ICT. The mainsimilarity across the countries is that education is by far the single most important factorlimiting the digitalization of low-income people. The impact of income was low althoughpositive. There is not apparently a gender gap in Colombia and Mexico but one in Peru.Our findings also suggest that when using a composite indicator that only include the`advanced ICTs´, disadvantage people among the low-income people can be moreconstrained in the use and access of more advanced information and communicationstechnologies.****El estudio analiza los determinantes de uso y acceso a las tecnologías de información ycomunicación en personas de bajos ingresos en pasases como Colombia, México y Perú. Elpunto central esta en analizar las diferencias entre países de acuerdo a diferentes variablessocioeconómicas. Se encuentra que la variable que más explica el nivel de acceso digital esla escolaridad. De otro lado no se encuentra una brecha por género sino en Perú. Losresultados también indican que cuando solo se tienen en cuenta las tecnologías más`avanzadas´, las diferencias entre la población son más notorias.Digital divide, ICT, gender gap, Internet

Expansions and Contractions in Some Latin American Countries: A view Throught Non-Linear Models

The study of the asymmetric behavior of macroeconomic variables over the business cycles phases has had a long tradition in economics. In this work we find evidence in favor of the hypothesis of having a Star-type nonlinear asymmetric behavoir of the economy activity, over the last two decades, in four Latin American countries: Brazil, Chile, Colombia and Mexico. For Venezuela the null hypothesis of a linear process could not be rejected under the method placed by Granger and Terasvirta (1993). Economic activity is proxied by monthly based industrial production indexes. Except for the case of Mexico we arrive to asymmetric representations of the processes. However, evidence of asymmetric behavoir is found according to the impulse response function analysis for all the countries.Real industrial production index, nonlinearties, STAR models, impulse responses

Multivariate Bayesian semiparametric models for authentication of food and beverages

Food and beverage authentication is the process by which foods or beverages are verified as complying with its label description, for example, verifying if the denomination of origin of an olive oil bottle is correct or if the variety of a certain bottle of wine matches its label description. The common way to deal with an authentication process is to measure a number of attributes on samples of food and then use these as input for a classification problem. Our motivation stems from data consisting of measurements of nine chemical compounds denominated Anthocyanins, obtained from samples of Chilean red wines of grape varieties Cabernet Sauvignon, Merlot and Carm\'{e}n\`{e}re. We consider a model-based approach to authentication through a semiparametric multivariate hierarchical linear mixed model for the mean responses, and covariance matrices that are specific to the classification categories. Specifically, we propose a model of the ANOVA-DDP type, which takes advantage of the fact that the available covariates are discrete in nature. The results suggest that the model performs well compared to other parametric alternatives. This is also corroborated by application to simulated data.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS492 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Entropy of entanglement between quantum phases of a three-level matter-radiation interaction model

We show that the entropy of entanglement is sensitive to the coherent quantum phase transition between normal and super-radiant regions of a system of a finite number of three-level atoms interacting in a dipolar approximation with a one-mode electromagnetic field. The atoms are treated as semi-distinguishable using different cooperation numbers and representations of SU(3), variables which are relevant to the sensitivity of the entropy with the transition. The results are computed for all three possible configurations ({\Xi}, {\Lambda} and V ) of the three-level atoms.Comment: 17 pages, 13 figure