Economist Zachary Karabell discusses his new book Superfusion: How China and America Became One Economy and Why the World's Prosperity Depends on It.

China's emergence as an economic superpower is widely recognized, but that is only one aspect of the story. Over the past decade, the Chinese and U.S. economies have fused—and this new dynamic to the superpower relationship will determine whether the coming decades witness increased global prosperity or greater instability.

Karabell traces the Chinese policy of aggressive economic reform and courting of U.S. companies back 20 years, coinciding with the Tiananmen Square protests in 1989. This economic fusion has enhanced the global economy while undermining the sovereignty that governments so crave—yet, the fusion has advanced too far for either nation to extricate itself without severe harm.

Zachary Karabell is president of River Twice Research, an independent economic research and consulting company. He sits on the board of the New America Foundation and the World Policy Institute, and in 2003 the World Economic Forum designated him a "Global Leader for Tomorrow." He is the author of nine books and his commentary appears regularly in the Wall Street Journal, New York Times, and Financial Times.