Asian stock markets have been sliding, and concerns that Greece will exit the eurozone have sent them into a further slump. But regardless of whether Greece leaves or stays, China, Japan and India all face serious problems.A generation ago Japan was the big Asian success stories, and young people today won’t believe it, but Americans in 1980 worried about Japan (and many wise pundits told Americans that we had to imitate Japan) in much the same way that people talk about China now. Then came thirty years of Keynesian stimulus, and thirty years of economic stagnation. The New York Times reports that Fitch has just downgraded Japanese sovereign debt ratings from AA to A+: a ranking just above Spain and far lower than the top grade of AAA. The outlook is negative, and Japan may see its debt downgraded further before long. Making matters worse, Japan’s exports are lower than expected, opening up a large trade deficit, according to Bloomberg. This would be a serious blow to a country that has historically depended on a robust export sector — and Japanese exporters once looked unbeatable.India’s economy is weak enough that some are calling it “the Greece of Asia.” The BBC reports that the Indian rupee has fallen to a historic low of 55.82 against the dollar, the tail end of a 26 percent slide that began late last year. This threatens to spur inflation and, with the coalition government paralyzed, there is not much sign of the leadership India needs to get back on the path to fast growth.China has managed to weather the economic storm better than many of its neighbors, but the signs of trouble in China are growing. A recent World Bank report revised its growth forecast for 2012 down to 8.2 percent from an earlier estimate of 8.4 percent, according to the FT. Even this relatively small shift will raise eyebrows in Beijing, which relies on rapid growth to keep a lid on increasing social unrest. China’s growth has been decelerating for some time; we are now in the range at which many China hands think that further deceleration could lead to some kind of social explosion.Europe’s troubles are hogging the headlines these days, and understandably so, but in the long run the troubles in Asia could have a much bigger impact on the way the world works.The United States, the EU and the great Asian economies are still wobbly; the global economic situation remains shakier than we could wish.