In the five years since the financial crisis crippled the American economy, a favorite warning of those who have urged forceful government action, myself included, has been that the United States risked entering a long period of “Japanese-style malaise.” Japan’s two decades of anemic growth, which followed a crash in 1989, have been the quintessential cautionary tale about how not to respond to a financial crisis.

Now, though, Japan is leading the way. The recently elected prime minister, Shinzo Abe, has embarked on a crash course of monetary easing, public works spending and promotion of entrepreneurship and foreign investment to reverse what he has called “a deep loss of confidence.” The new policies look to be a major boon for Japan. And what happens in Japan, which is the world’s third-largest economy and was once seen as America’s fiercest economic rival, will have a big impact in the United States and around the world.

Of course, not everyone is convinced: though Japan reported a robust 3.5 percent annualized growth rate for the first quarter of this year, the stock market has dipped from a five-year high amid doubts about whether “Abenomics” will go far enough. But we shouldn’t read anything into short-term stock fluctuations. Abenomics is, without a doubt, a huge step in the right direction.

To really understand why things look good for Japan requires not only looking closely at Mr. Abe’s platform, but also re-examining the popular narrative of Japanese stagnation. The last two decades are hardly a one-sided story of failure. On the surface, it does look like there’s been sluggish growth. In the first decade of this century, Japan’s economy grew at a measly average annual rate of 0.78 percent from 2000 to 2011, compared with 1.8 percent for the United States.

BUT Japan’s slow growth does not look so bad under close examination. Any serious student of economic performance needs to look not at overall growth, but at growth related to the size of the working age population. Japan’s working age population (ages 15 to 64) shrank 5.5 percent from 2001 to 2010, while the number of Americans of that age increased by 9.2 percent — so we should expect to see slower G.D.P. growth. But even before Abenomics, Japan’s real economic output, per member of the labor force, grew at a faster rate over the first decade of the century than that of the United States, Germany, Britain or Australia.