Italian and Eritrean migrant boys play football in Lampedusa, Italy, near a harbor filled with boats used by migrants for one-way trips from Africa to Europe. (Tullio M. Puglia/Getty Images)

More than 300 would-be immigrants died just a mile off the coast of the Italian island of Lampedusa on Thursday, when the boat carrying them from North Africa's coast caught fire and capsized. The incident has drawn new attention to the huge numbers of illegal immigrants crossing the Mediterranean from Africa to Europe -- and how many of them die along the way.

World Bank economist Branko Milanovic sees incidents like this one, and the death toll among African migrants headed toward Europe -- as well among Latin American migrants crossing into the United States -- as a function of global inequality and its changing role in the world. In his 2012 book, "The Haves and the Have-Nots: A Brief and Idiosyncratic History of Global Inequality," Milanovic wrote, "In an unequal world where income differences between countries are large, and information about these income differences is widespread, migration ... is simply a rational response to the large differences in the standard of living."

But, as rich countries fight to keep migrants out and poorer countries struggle to keep them from leaving, hundreds die on these crossings every year, and "a conspiracy of silence from both sides envelops the dead," the economist writes. And it's getting worse. I spoke with Milanovic over the phone about the incident near Lampedusa, immigration, borders and inequality.

WorldViews: What did the incident off Lampedusa say, to you, about immigration across the African and European Union borders?

Branko Milanovic: As you may know, my book spends quite a lot of time discussing the income gaps between the countries. And of course these income gaps, historically, have risen tremendously, despite the fact that in the last 15 or 20 years, China and India have grown at very high rates. Still, the number of countries in Africa where income today is lower than in the 1960s [when they won independence] is large, I think about 15 countries.

So, clearly, the gap between Africa and Europe has increased. Even the gap between the United States and Mexico, for example in [gross domestic product at purchasing power parity], which is adjusted for price levels in each country, that gap has gone up. So the implication of that is that if the gap is significant, large, and in some cases rising, and the knowledge about the existence of such differences is more widespread, and the cost of transportation is less, then you will have huge pressure to migrate.

WV: And you talked about, as the European response to that, the "Mediterranean wall." What are European countries trying to do by stemming immigration?

BM: They have essentially a quasi-military effort on the borders in order to dissuade the boats [carrying migrants] coming across the sea. And they have an even deeper approach, in that they're trying to persuade Arab countries [along the North African coast] to take most of the African refugees or potential migrants and keep them there.

WV: In the data from your book, you compared the death rates among immigrants crossing the African-European border, the U.S.-Mexico border and the Berlin Wall. Why did you pick those three?

BM: In all three cases, you have impediments to the free movement of people or labor. In one case, it's an impediment for people to leave the country, and in the two other cases it's an impediment or obstacle for people to get somewhere else.

In one case you had an active attempt to stop people, to shoot them. In the other two cases, you don't have an active attempt to do that. But you might have a sort of dissuasive attempt, which in some cases like this tragedy that's just happened, coincides in terms of outcomes with what we've seen in East Germany.

WV: The efforts to stem migration across the Africa-Europen Union and the U.S.-Mexico borders are so different from the Berlin Wall. Does that difference say anything about how the world has changed?

BM: Of course the world has changed but there is sort of a basic issue there, to which there's no easy answer or easy solution, and that's the question of freedom of movement. We live in a world that is much more globalized, in which capital, knowledge, ideas and so on can travel much more easily. At the same time, it's a world in which people cannot move from country to country. So that is the core of the problem there.

Now, of course, you can say there are good reasons why people should not be allowed to move, there are arguments for that. People are a little bit different from capital, people in any given country are participants in a sort of political community. And they might decide to exclude certain people or not exclude them.

But it does raise an uncomfortable issue because all the other components of production are mobile, with the exception of one.

WV: But there've always been rich and poor countries, so something must be changing. What's different now?

BM: What's different now is that people are much more aware of the differences between countries. In the past, these restrictions did not exist. But you didn't have, in the 19th century, these numbers of people from Central Africa going to France. So what has changed is that people know about the differences much more commonly than they did before, and the ease of transportation is much greater.

WV: So it's not just that there's economic inequality between countries. But, in a sense, there's less distance. Is that true?

BM: I think you can actually argue that the economic difference has increased, that it's higher than what it was 100 or 150 years ago. But then this kind of psychological distance has shrunk, and travel costs have gone down.

WV: So what sort of role do these borders -- the "Mediterranean Wall," the U.S.-Mexico border fence -- play in this new kind of world?

BM: To some extent they play the same role that gated communities play within cities. It's about stopping people who you don't want from coming in. Of course the problem is not simple, and I do understand the European point of view. But there is a discrepancy on freedom of movement and a very clear attempt to de-emphasize this problem.

This is not a new problem. Since 1988, something like 20,000 or 25,000 people -- and actually nobody knows the real number -- have died [trying to cross from Africa to Europe]. And this attempt to ignore the problem is not only a European issue, it's also an issue for Arab countries. Before the Arab Spring, these regimes saw this migration as evidence of their own failure to provide their own young people with a future and with employment. So there was a sort of collusion, on both sides, to forget about the problem.

WV: Do you see more of these sorts of borders forming in other parts, for example in Asia, where some countries are getting richer and some are not?

BM: Yes. In Asia you have a similar problem between India and Bangladesh, where India has built up the border. You have a similar problem, without the border, with the periodic expulsion of Indonesians from Malaysia, where also the income gap is very large.

In the Middle East you have the border between Saudi Arabia and Yemen, which is actually a large fence. There the income gap is huge. And of course the border between Israel and Palestine.

There's also North Korea and South Korea, but that's a little bit different because it's politically motivated. And to some extent you could say that Israel-Palestine is politically motivated, but it's also economically motivated because the Palestinians can and do work in Israel.

WV: It's fascinating how these economic divides become political divisions as well.

BM: There are two issues there that are really interesting. First, it's the question of what globalization means for labor. And second, the gaps between the nations are rising along with the ability to know much more about each other and the ease of transportation across long distances. All of which are bringing the migration situation to a head.