The Fed's next chairman faces a troubling possibility that the new normal for the economy is even worse than thought, according to economists at JPMorgan Chase, reports Bloomberg.The long-run potential growth rate for gross domestic product fell to about 1.75% per year, from an average rise in GDP of 2.5% since 1990, the economists say. That would be the lowest level since World War II and below the 2% mark that PIMCO said is the new normal for the economy.