As 2015 starts, China's leaders should learn from the experience of Japan in 2014. There is mounting evidence that Japan may have squandered its best chance for a meaningful recovery in more than a decade.

The country is in recession again, foreign investors are losing confidence in Prime Minister Shinzo Abe's revival plan and deflation has returned. Last month the government approved a $29 billion stimulus package that it hopes will keep things from getting worse.

The travails of "Abenomics" should be a warning to President Xi Jinping of China, whose nation increasingly seems at risk of a Japan-like lost decade. Although speculation has focused on the "why" and the "how" of the Japanization of China's economy, the year ahead will provide clues to the question of "when."