Almost 10 years after the Great Recession ended, the growing threat of a new economic slowdown raises a troubling question: When the next recession strikes, what can the world’s central banks do? With interest rates low and their balance sheets still loaded with assets bought to fight the 2008 crisis, do they have the tools to respond? This column is one of five looking at that question.U.S. state governments suffered major damage from the last recession 10 years ago. During the second quarter of 2009, the final months of the downturn, personal income taxes tumbled 27 percent from a year earlier.