Japans silver pacifism.

• Author: Funabashi, Yoichi
• Position: Essay

The future that has already happened." That is how Peter Drucker described the relevance of demographics. Around the world, policy makers are starting to agree, and governments are taking unprecedented steps to prepare for the next generation. After more than three decades, China has abolished its one-child policy in a dramatic departure from a core Communist Party position. The Japanese government under Prime Minister Shinzo Abe has set the country's first numerical target to stabilize the population at 100 million over the next 50 years, breaking a postwar political taboo. A consensus is reemerging that demographic trends are a crucial factor determining the fate of nations.

Japan is in the midst of a silently unfolding crisis. The figures are staggering. The country's population peaked in 2008 at around 128 million and has been in decline ever since. Today, there are fewer than 127 million people in Japan, and its population is falling by nearly three hundred thousand a year, according to the National Institute of Population and Social Security Research. By 2040, Japan could be losing one million people a year. These numbers add up. By the end of the century, Japan's population could fall to as little as fifty million--equivalent to what it was in the early 1900s. Japan is also the fastest-aging society in the world. Its working-age population peaked in 1995, and today one in four Japanese is over the age of sixty-five. By 2050, it could be two of every five.

At the same time, Japanese are having fewer children than before. In 1990, the country experienced what has been termed the "1.57 shock," when the fertility rate dropped to its lowest level yet. Since then the fertility rate has fallen further, to around 1.4, well below the replacement rate of about 2.1 births per woman. There are few signs that this will improve. Belated pronatal government policies, such as tax incentives and attempts to make more childcare facilities available, have been largely ineffective, while a growing proportion of the population is delaying marrying or opting to become "lifelong singles," which generally means fewer children. Globally, Japan is being recognized for the wrong things--a country with sexless youth, more registered pet cats and dogs than children under fifteen, and a market in which adult diapers outsell baby nappies. But beyond the negative consequences for the Japanese brand, the geopolitical implications of these demographic shifts are profound.

Historically, societies have been concerned with population growth and with the survival of their likeness. Religions have called for humans to "be fruitful and multiply." Nations, in particular, fear population decline, as it is believed to be a harbinger of national weakness and defeat. Japan is no exception, and the nation should be weary of becoming marginalized in regional and global affairs. By 2050, Japan stands to lose its seat among Asia's "population G7"--a grouping that will then consist of India, China, Indonesia, Pakistan, Bangladesh, the Philippines and Vietnam. To be sure, a large population doesn't guarantee an increase in regional stature, but history has yet to provide an example of a declining population that is able to significantly build on its clout. If Japan is serious about being a leader in shaping the future Asia-Pacific regional architecture as a liberal-democratic state, it must not only concern itself with moral authority, but it must also be conscious of the regional population dynamics.

In 1904, Sir Halford Mackinder, the father of modern geopolitics, wrote, "Man and not nature initiates, but nature in large measure controls." Demography is the underlying determining factor that poses the principal challenge to Japan's national revitalization and attempts to overcome the legacy of its lost decades. The impending population bust threatens to undermine not only the success of Abenomics, but also the future of defense-policy reforms. It will deepen security risks and could ultimately result in Japan's marginalization in the Asia-Pacific.

Population is power. After the devastating defeat in World War II, Japan benefited from a "demographic bonus" that paved the way for the nation's economic growth and reemergence on the world stage. Conversely, since the 1990s a "demographic onus" has intensified its financial plight. Japan's population...