According to the BBC, one in five Irish homes is vacant. This glut of housing is a symptom of the truly gigantic building boom that hit Ireland in the early 2000s: Guest workers from all over Europe flocked to rural areas around the country, where speculative housing projects were popping up in droves. But just a few years later, as the global financial crisis took hold, it became clear that the demand just wasn’t there. In 2006, Irish economist David McWilliams named these developments “ghost estates,” and the name has stuck.