The mileuristas are those Spaniards born approximately between 1965 and 1985 (generation X in the USA). I don’t know how Spain has a GDP as high as it does, but the average salary is something like 1,600 Euros a month and about 58% of the population lives off less than 1,100 a month. A lot of people (mostly immigrants and the young) make a minimum wage of 700 E a month, which you get for any regular cafe job, and can demand any number of hours.
Add to that the fact that there is over 20% unemployment overall, and over 40% for the youth, and you’ve got the perfect recipe for a lost generation of the middle class that won’t be able to afford a flat, children, vacations, etc.
So what do middle class kids do instead? Study, a long, long time—meaning that competition is high, and you have to study even longer. They live at home until they get married, often into their 30’s. And, reversing the trend of a few decades of in-migration, they are beginning to move abroad again. A similar phenomenon is occurring in Ireland and Portugal, also nations which, after decades of sending people abroad, got rich rapidly (and unstably), then crashed, and have now returned to become exporters of their young and bright. Not many, apparently, want to end up still a mileurista well into their thirties, though they often have no choice.
The other option for the young and middle class (only option?) is to persevere in school, pass their tests, get their Master’s degrees and try to find a government job. A typical Spaniard doest want to deal with the hectic business world. It’s not very friendly, high-paying, or secure, in Spain, so they aspire instead to become a funcionario, jobs which tend to push out any more productive jobs and indirectly cause high unemployment. It’s a vicious circle, one of the several that afflict the smaller nations of Europe.