An E.U. flag flies near the Parthenon in Athens. (Bloomberg)

The Nobel Peace Prize this year went to the European Union, which prompted cackles at a time when the E.U., or at least its common currency, appears on the brink of collapse. "When did Tina Brown start handing out Nobel Peace Prizes?" cracked The Atlantic's Matt O'Brien. "Nobel committee congratulates Germany on over 70 years without invading France," quipped University of Denver political scientist Seth Masket.

But the case for the prize is stronger than the snark would have you believe. Here are five of the best reasons why the E.U. deserved it.

 1. But seriously, Germany hasn't invaded France in over 70 years.

Masket was joking, but there is good reason to believe that the E.U. contributed to the remarkable 70-year period of peace in Western Europe. No Western European country has gone to war with another since World War II, and the Balkans wars were the only wars on the continent as a whole in that period.

Now, some of that is surely due to the Cold War uniting Western Europe in opposition to the Soviet Union. But that doesn't explain all of it. As George Washington University's Henry Farrell notes, there's good reason to think the E.U. played a key role in securing peace in Europe in the 1990s. Farrell points to a study by Thomas Diez, Stephan Stetter and Mathias Albert arguing that the E.U. played a role in arbitrating border disputes in a nonviolent manner, as well as two studies, one by Farrell and Gregory Flynn and another by Jeffrey Checkel, arguing that the union's membership requirements helped push former Soviet satellites and possessions toward democracy (more on why spreading democracy in that region helped peace later on).

This all sounds intuitive today, but it wasn't when the Soviet Union was collapsing. The University of Chicago's John Mearsheimer, one of the most respected "realist" international relations scholars currently working, wrote a famous paper in 1990 predicting that Europe was about to return to its old warlike ways. Appropriately titled "Back to the Future," the paper predicted that Germany, France, the U.K. and potentially Italy would become major powers, with Germany and the Soviet Union warring over control of Eastern Europe, and Hungary and Romania likely going to war. It suggested giving Germany nuclear weapons to deter such conflict; Mearsheimer later suggested that Ukraine get them as well.

The point being, it was not at all obvious in 1990 that Europe's pattern of peace would last without the Soviet Union to unite against. And yet it did.

2. It made the continent — especially poor countries — richer. And that stopped war.

"Well, of course," you might think. "It's a rich democratic region. Those don't tend to be warzones." That's true, but in many ways Europe is as rich as it is because of the E.U. Starting with the European Coal and Steel Community, and later, the European Economic Community, the process of European integration dramatically reduced tariffs and other trade barriers between countries. As Berkeley's Barry Eichengreen noted in 1992, as the EEC was becoming the E.U., economists generally agree that regional integration like that can spur growth. Multiplerecent studies have confirmed this, one of which estimated that per-capita income in E.U. member states would be one fifth lower without European integration.

Another found that trade increased more among poorer "periphery" states and between them and rich "core" states than it did among the core states. That suggests that poorer, Eastern European members drew most of the economic benefit. A 2008 paper found that expansions of the E.U. in 2004 and 2007 greatly increased immigration from poor to rich countries, which helped growth in the continent as a whole.

There's a large amount of empirical literature, ably summarized by Columbia's Erik Gartzke here, suggesting that better economic conditions prevent war. That's intuitive, and the idea dates back to Kant's "Perpetual Peace." For one thing, good economic conditions prevent "diversionary wars" that states launch in an attempt to distract from bad economic conditions. As preposterous as it may sound, those wars do occur, with Argentina's invasion of the Falklands during bad economic times a prime example. In particular, Yale's Bruce Russett and Harry Bliss found that trade between states greatly reduces the chance of war.

Evidence suggesting that European integration has greatly increased per-capita income and trade between member states, then, suggests that it has also reduced the chance of war.

3. It has spread democracy, and democracies don't fight each other.

This is a matter of some controversy, but there is widespread belief among international relations scholars in the "democratic peace." Democracies and dictatorships fight a lot, and dictatorships fight each other all the time, but it's hard to single out a case of a democracy fighting another democracy.

There are a few boundary cases — such the Kargil war between Pakistan and India in 1999 (Pakistan was a democracy but not a strong one) and World War I (Germany and the U.K. both had powerful parliaments, though less for the former). But even conceding those, the likelihood of conflict between democracies is still much lower than between democracies and non-democracies or between dictatorships. In one of the most-quoted lines in all of international relations, Rutgers' Jack Levy proclaimed that the democratic peace "comes as close as anything we have to an empirical law in international relations."

So if the literature that Henry Farrell mentioned (and contributed to) is correct, and the E.U. promoted democracy among ex-Soviet satellites and imperial possessions in Eastern Europe by requiring democratic practices as a prerequisite to membership,  then it in a small way contributed to peace in the region as well.

Caveats are in order, though. Some argue that there haven't been enough democracies in history to draw strong conclusions about the effect of democracy on states' behavior. What's more, they claim that since the rise of democracy coincided with the Cold War, for which most democracies were on one side, one cannot conclude that democracies cause each other not to fight. But some, like John Oneal and Bruce Russett, have found statistically significant results confirming a democratic peace even before the Cold War, blunting that criticism.

In sum, I'm inclined to agree with Levy. The democratic peace is well enough established to credit institutions like the E.U. that promote democracy with reducing the probability of conflict, at least among its members.

4. It started a process that will keep hurtling toward more integration.

Georgetown's Erik Voeten highlights the work of the late Ernst Haas and other "functionalists" who argued that institutions promoting integration like the E.U. create spillover effects that in turn lead to yet more integration and so on. For example, the initial success of the European Coal and Steel Community lead to demands for economic integration in other areas, leading eventually to the European Economic Community. This implies that European integration has a momentum of its own, so trade and political integration will only grow.

That means good things for peace. As shown above, trade between two countries greatly reduces the chances they'll fight each other, so if Haas and functionalism are correct, then the benefits of European economic integration to peace will just keep growing. What's more, the logical endpoint of the process described by Haas is a European super-state. There is a possibility of civil war within such a state, but if successful, it would effectively eliminate the possibility of war in Europe, just as the successful integration of the United States after the Civil War has lead to 150 years of peace within the country.

5. It makes people think of themselves as Europeans.

Voeten points to another study, by Liesbet Hooghe and Gary Marks at the University of North Carolina, which found that Europeans who claim a "strong national identity" are more, rather than less, likely to identify with the European project. That suggests that people are starting to include being European as part of their national identity, in addition to being French, German, Italian, etc. Jack Citrin and friend-of-Wonkblog John Sides have found that the proportion of Europeans identifying with Europe, either exclusively or in addition to their home country, increased by 13 points in the 1990s.

This kind of identification could decrease the propensity of Europeans to fight other Europeans, on the grounds that they share a common identity. Wars between actors who share a common identity do occur, as in the Palestinian civil war between Hamas and Fatah, but they're much rarer than intergroup conflicts. So if more and more Europeans are thinking of themselves as Europeans as well as Frenchmen, Italians, etc., that could bode well for peace within the continent.