Consumer sentiment in the U.S. has unexpectedly seen a continued improvement in the month of May, according to a report released by Reuters and the University of Michigan on Friday, with their consumer sentiment index jumping to a four-year high. The report showed that the consumer sentiment index rose to 77.8 in May from the final April reading of 76.4. The increase came as a surprise to economists, who had expected the index to edge down to 76.2.