However, in the Czech Republic, Denmark, Iceland, Luxembourg, the Netherlands, Poland and Switzerland, more than 40% of 19-year-olds are still enrolled in secondary education. These high shares may partly be explained by the structure of the education system and the strength of the labour opportunities offered by vocational upper secondary programmes in these countries, making them more attractive than tertiary education. Enrolment of 19-year-olds in tertiary education averages 34% across OECD countries, ranging from 2% in Luxembourg (the low share is due in large part to the high number of students studying abroad) and 3% in Iceland to 73% in Korea.