This being an English-speaking Spanish property forum, it is bound to be peopled by commentators who have left their homelands at some stage to live and work abroad, or are actively considering such a move.
As English speakers we are unlikely to have moved to Spain because of poverty or lack of opportunity back home, because we come from comparatively wealthy countries, but the majority of incomers to Spain will have come from poorer countries, from Eastern Europe or South America, or Northern Africa.
For many reasons Spain has sunk deeply into recession over the past five years, with no immediate end in sight, and young Spanish people are now emigrating in vast numbers to find work in countries where there is employment for them, countries like Germany and the UK.
This mass movement of people is not new, and there is no need to delve too far into history because it gets complicated, but Turkish people moved to Germany, and Jamaican people to the UK, purely to find work.
A curious side effect is that a lot of them stayed on and built their lives in their new countries. The same could happen to Spanish people who are on the move now.
(To return to Spanish property, if the country is emptied of its own nationals and immigrants from poorer countries return home, who on earth is going to buy all the empty houses?)