Daniel Griswold, with an assist from the Democratic Leadership Council:

“Peace on earth, good will toward men” is a phrase we associate with the Christmas season. One bit of good news that you will probably not see in the newspaper or on cable TV over the holiday is that the world in recent decades has actually been moving closer to that ideal, and free trade and globalization have played a role.
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There are two main ways that globalization promotes peace: The growing network of global trade and investment has raised the cost of war, so that now if two nations go to war, they not only lose soldiers and tax dollars, they also lose markets and cause lasting damage to their economies. Globalization has also reduced the spoils of war by allowing people to acquire resources through peaceful exchange rather than conquest.

The DLC Trade Fact memo shares the credit with decolonization, the end of the Cold War, the spread of democracy, and peacekeeping missions, while also recognizing the contribution of economic openness:
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Eliminating all remaining trade barriers would be one of the best Christmas presents our politicians could give us.