It's the rare economic tale that involves suicides, robots and arms dealers. Welcome to Japan, where science fiction may begin to trump economic fact in ways the global audience has yet to realize.

That's not what the financial headlines suggest. As the press put 2016 to bed, the narrative was of fresh vigor: a weaker yen boosting exports, the Bank of Japan upgrading growth prospects, Nikkei stocks on a tear, Prime Minister Shinzo Abe friending Donald Trump. There's one problem with this plot and it's called a calculator.

From his perch in New York, Richard Katz finds something isn't computing: how a shrinking, aging, baby-starved and highly indebted nation generates 0.5 percent growth on a sustainable basis. Japan surely can if, and only if, it drastically raises productivity. If it can't, Katz argues, the No. 3 economy will have zero per capita gross domestic product growth for another 45 years, or so.