Four-yearly Wage Structure Survey Four-yearly Wage Structure Survey. 2006 Variation coefficients for the gross annual earnings by studies Unidades: % All studies,0,45, I. Without studies,1,42, II. Primary education,1,43, III. Secondary education I,0,72, IV. Secondary education II,1,34, V. Intermediate vocational training,1,03, VI. Advanced level vocational training,0,91, VII. University diploma or equivalent,1,67, VIII. University graduates, advanced engineers and doctors,1,13, Notas: Fuente: National Statistics Institute