In 1993, the linguist Scott A. Schwenter published a study of tú and usted in the Nueva Revista de Filología Hispánica of El Colegio de México. His Mexican informants were middle-class adults in Mexico City. They chose tú in 32 percent of their answers. The study found that they tend to use usted with people of every age group.
The sample was small, 18 informants, and the data are more than 30 years old.