There has been plenty of discussion lately about signs that China’s economy is slowing down, focused on details of a possible housing bubble and vast sums of bad loans that the country will have to reckon with. But put aside the challenges China faces this quarter, or next year, and there is one view that is overwhelming: China is a long-term economic juggernaut that will stand astride the global economy in another generation’s time.

I know this because, for years now, major magazines and editorials and books have told me about the Chinese Century, in which we are apparently now living. Leading foreign policy journals have devoted copious ink to exploring what China’s rise will mean for global economics and politics, often taking as a given that China will be the dominant power of the coming century. (“Can the Liberal System Survive?” Foreign Affairs asked in 2008.)

Official forecasts — from international agencies like the Organization for Economic Cooperation and Development and the World Bank, and from United States intelligence circles — envision China continuing to grow rapidly over the next couple of decades, its economy eventually becoming much larger than that of the United States. Robert W. Fogel, a Nobel laureate in economics, forecast in 2010 that in 2040, Chinese economic output would be $123 trillion, about seven times the current size of the American economy (and three times his forecast for the United States in 2040).

But what if it’s all hogwash?

Many of the most bullish forecasts of China’s economic future are based, more or less, on extrapolation. For more than three decades, its economic output per person has been rising at an extraordinary annual rate of 6 to 10 percent, climbing rapidly toward levels in the richest nations. If that continues for a couple of decades, the bullish forecasts will prove accurate.