The U.S. is seeing the biggest spike in demand for cold, hard cash since the Y2K “bug” panic of 1999, as customers of U.S. banks and credit unions have made big withdrawals to brace themselves for coronavirus fallout. According to data by the Federal Reserve, the number of banknotes in circulation rose by $35 billion, from $1.808 trillion on March 11 to $1.843 trillion on March 18.