These categories were further grouped as follows: high class, I+II; middle class, III; and lower class, IV + V. Total household income was categorized as the following: less than 600 €/month; between 601-1200 €/month; 1201-3600 €/month; more than 3601 €/month; or did not answer.
Posteriormente, dichas categorías se agruparon en: clase alta: I+II; clase media: III y clase baja: IV + V y los ingresos totales del hogar menos de 600€/mes; entre 601-1200€/mes; 1201-3600 €/mes; más de 3601€/mes; no contestó.