It is impossible to ever be completely certain why people do what they do. We ourselves are unsure as to why we acted in one way or another. Motivation is a strange beast. Our lives are mysteries that we only begin to unravel when we have some distance (measured in years or decades) and can look back to make some sense of the patterns and defining choices that put us right here, right now, in this place. It may be that what we think is less reliable then what we feel. I would be very suspicious of any poll that reported the "real reasons" people migrate. Studies may be more reliable but the ones I have read are very limited in scope, "The Mexican-American Experience", for example, or "British International Retirement Migrants in Spain" or "Chinese-Canadian Managers in Shanghai." Since there is so little reliable information, migration is a blank slate upon which people write their own narratives and impute motives to migrants that have everything to do with natives' own inner turmoil and very little to do with the migrants themselves.
There is no one answer to the question, "Why did you/they leave?" In some cases migration is involuntary - borders change, wars break out and stateless people are cast upon the mercy of other states willing to receive them. These migrants had their decisions made for them. They had to leave or can only stay under conditions that are hostile and precarious. Even today there are more people than you might think in this position and their stories are tragic and heartbreaking. Nearly 680,000 in Europe alone at the beginning of the 21st century. That story merits its own post so for now we'll restrict our discussion to voluntary migration.
For the voluntary migrant a decision to migrate is made based on an evaluation of the opportunities and constraints in the home country, the attractiveness of certain destination countries and the individual's personal context. Bear in mind that the potential migrant is almost always making this decision with limited information. No migrant knows for sure what life is really like in the destination country. It is a leap into the dark, an act of faith, a gamble. Here are a few of the factors I thought of that go into evaluating the migration equation:
Opportunity: Sometimes it is as simple as believing that there are better jobs that pay more elsewhere. This is true of workers but it is equally true of skilled or executive labor. An expatriate businessman or woman may choose to accept an assignment overseas because he may enjoy a higher standard of living in a destination country and be able to save money to bring back home. For other people the draw may be the ease of starting a business or because they are held back at home because of racial or gender discrimination. In Leaving America by John Wennersten, he devotes an entire chapter to the exodus of African-Americans to Europe, Asia and Africa. I know North African women in Paris who left home because they felt limited in spite of their advanced academic credentials and work experience. Many countries even advertise opportunities hoping to attract people. Go to Google and type in "Teaching English in Korea," and see how many hits you get. Sweden has this site, Three Good Reasons to Work in Sweden. Escapeartist has an entire page devoted to finding overseas jobs. See this video, Coming to Australia, about working and living in the Land Down Under. A quick pass through these sites show that there is as much "pull" as there is "push".
Networks: Despite all the advertisements, no migrant really knows if he or she will fare better somewhere else but one way that migrants hedge their bets is by using social networks to gather information and to ease into life in a new land. A lot has been written about the Overseas Chinese network but nearly all countries have established immigrant communities that will help new migrants get established in the host country. In France, for example, the Portuguese community is very strong. In Multi-Ethnic France: Immigrants, Politics, Culture and Society, Alec Hargreaves writes, "On a per capita basis the Portuguese population is believed to have a denser network of voluntary associations than any other minority group in France...This, together with the relatively generous provision of state support for mother tongue teaching, and the geographical proximity of Portugal, which makes it easy for families to pay regular visits to the home country, has enabled the Portuguese to maintain closer cultural ties than many other groups of recent immigrant origin." Another example would be the large communities of American retirees in Mexico who send back news about the good life south of the border and encourage others to come on down.
Adventure: I cannot count the number of people I have met who want to do the "Peter Mayle thing." For some people there is something delightful about selling everything and relocating to an exotic land to build a new life in a new language. After business reasons, this is, I think, the primary reason that people from developed countries in America and Europe leave home. For Americans this taps into something very deep in the American psyche: the desire for new frontiers that drove previous generations farther and farther across the continent until they reached the Pacific Ocean. Today there are very few frontiers in the U.S. I think John Wennersten is absolutely right when he says, "The same types of people who used to move to Montana or Alaska to escape are now moving to Mexico, Canada and beyond...In the current atmosphere of cultural flux, downsizing, and diminished opportunities, things seem better in Budapest than Buffalo." Other people have similar reasons. I know French people in Tokyo who are in love with Japan and find the idea of returning to France rather boring after living in such a beautiful, exotic and gracious land. I've talked to Brits who have the same feeling about France - they have successfully installed themselves in small villages all over the countryside and find it and the people wonderful. People who go for adventure take the economic environment into consideration but it's not the primary motivation. Many are willing to take low-paying jobs in exchange for a chance to do something interesting and different in a foreign land.
André Aciman wrote, "expatriation, like love, is not only a condition that devastates and reconfigures the self; it is, like love, a trope, a figure with which we try to explain, try to narrate profound psychological disruptions in terms of very measurable entities: a person, a place, an event, a moment, etc."
I believe that migration is central to the human experience. It devastates and recreates. It is both a deeply personal decision and a path that was tread by all our ancestors at one point or another. I don't believe for a moment it can be stopped and I am very dubious about efforts to control it. States can put up barriers, increase deportations and spend millions, if not billions, of euros turning their countries into fortresses but no power on this earth has ever prevented people from dreaming and acting on their hopes and aspirations.