Four-yearly Wage Structure Survey Sampling errors Studies completed. National total Units: % All studies,0.37, I. Without studies,3.90, II. Primary education,1.43, III. Secondary education I,0.90, IV. Secondary education II,1.35, V. Intermediate-level vocational training,1.39, VI. Advanced vocational training,1.32, VII. University diploma-holders or the equivalent,1.39, VIII. University graduates, advanced engineers and doctors,1.37, Notes: Source: National Statistics Institute