HONG KONG — China has bought more than $1 trillion in American debt, but as the global downturn has intensified, Beijing is starting to keep more of its money at home – a shift that could pose some challenges to the U.S. government in the near future but eventually may even produce salutary effects on the world economy. At first glance, the declining Chinese appetite for U.S. debt – apparent in a series of hints from Chinese policy makers over the past two weeks, with official statistics due for release in the next few days – comes at an inopportune time. On Tuesday, the U.S. president-elect, Barack Obama, said Americans should get used to the prospect of ‘trillion-dollar deficits for years to come’ as he seeks to finance an $800 billion economic stimulus package. Normally, China would be the most avid taker of the debt required to pay for those deficits, mainly short-term Treasury securities. In the past five years, China has spent as much as one-seventh of its entire economic output on the purchase of foreign debt – largely U.S. Treasury bonds and American mortgage-backed securities. But now, Beijing is seeking to pay for its own […]