1. UC Davis, Department of Statistics , Davis, California, 95616–5270, U.S.A.
2. National Department of Statistics , Population projections division, Bogota , Colombia .
3. The Miguel Hernández University of Elche (UMH) , Centro de Investigación Operativa, Departamento de Estadistica , Matemáticas, Avenida de la Universidad s/n ELCHE, 03202 , Spain .