Famed economist David Rosenberg warned that the U.S. economy may be headed for a crash landing in a tweet last week. Rosenberg is the president and chief economist of Rosenberg Research. He was previously chief economist and strategist at private wealth management firm Gluskin Sheff and chief North American economist at Merrill Lynch in New York. The Philadelphia Fed Manufacturing Index is based on the monthly Business Outlook Survey of manufacturers in the Third Federal Reserve District, which is home to over 13.3 million people in Delaware, southern New Jersey, and eastern and central Pennsylvania. The survey has been conducted each month since May 1968. The index in the U.S. ticked up 1 point to -23.2 in March.