The outrage of the young has erupted, sometimes violently, on the streets of Greece and Italy in recent weeks, as students and more radical anarchists protest not only specific austerity measures in flattened economies but a rising reality in Southern Europe: People like Ms. Esposito feel increasingly shut out of their own futures. Experts warn of volatility in state finances and the broader society as the most highly educated generation in the history of the Mediterranean hits one of its worst job markets…

Giuliano Amato, an economist and former Italian prime minister, was even more blunt. “By now, only a few people refuse to understand that youth protests aren’t a protest against the university reform, but against a general situation in which the older generations have eaten the future of the younger ones,” he recently told Corriere della Sera, Italy’s largest newspaper…

Indeed, experts warn of a looming demographic disaster in Southern Europe, which has among the lowest birth rates in the Western world. With pensioners living longer and young people entering the work force later — and paying less in taxes because their salaries are so low — it is only a matter of time before state coffers run dry.

“What we have is a Ponzi scheme,” said Lawrence Kotlikoff, an economist at Boston University and an expert in fiscal policy.