Four-yearly Wage Structure Survey Sampling errors Studies undertaken. National total Unidades: % Both sexes Females Males All studies "" "" "" I. Less than Primary "" "" "" II. Primary education "" "" "" III. First stage of secondary education "" "" "" IV. Second stage of secondary education "" "" "" V. Higher-level vocational training courses and similar "" "" "" VI. University graduates and the like "" "" "" VII. Graduates and similar, and university doctors "" "" "" Notas: Fuente: