The OECD's 'Education at a Glance 2013' study, published on Tuesday, reveals that one in four Spaniards aged 15–29 who have completed tertiary education, such as vocational training or the Bachillerato, are NEET — or neither employed nor in education or training.
The 24.4 percent of young Spaniards who find themselves in this position was much higher than the OECD average of 15 percent.
More worryingly, the 69 percent jump in Spanish NEETs between 2008 and 2011 was also considerably sharper than the 24 percent increase seen across the OECD as a whole.
NEETs are known in Spain as 'ni-nis' (ni estudian ni trabajan , or 'neither working, nor studying') and have been described as a 'lost generation', who have failed to find opportunities because of Spain's economic crisis.
The OECD report also noted that young Spaniards aged from 15 to 29 "are expected to spend more time in education (6.4 years) than in employment (5 years)".
This remains, however, shorter than the OECD average of 7.1 years.
The organization also highlighted Spain's relatively higher average periods of inactivity (1.1 years) and unemployment (2.5 years): the OECD average for unemployment is 2.4 years.
Spain joined Italy, Mexico, Portugal and Turkey as one of only five OECD countries where less than 60 percent of people aged 25–64 have attained an upper-secondary or tertiary education.
The average across the OECD is 75 percent.
Although the report covers only the 2008–2011 period, Spain's rising unemployment rates were already evident.
Unemployment in Spain hit 27 percent in 2013, the highest level in 37 years.
But the OECD also showed educational level offered some protection against unemployment.
Despite all three rates being higher than the OECD averages, the report noted that "these rates confirm that at higher levels of attainment people are less exposed to unemployment and have better chances to keep participating actively in the economic system, for the benefit of both individuals and society".
The authors added: "The difference in unemployment rates between adults with lower and higher levels of education is particularly large in Spain, as well as the Czech Republic, Estonia, Hungary and the Slovak Republic."