The U.S. economy may be on the verge of -- or already in -- a recession, based on the increase in 2007's unemployment rate, economists said. The jobless rate rose to 5 percent in December, the highest in two years. The figure was 0.6 percentage point higher than March's 4.4 percent, which was the lowest reading of the expansion that began at the end of 2001. ``Since 1949 the unemployment rate has never risen by this magnitude without the economy being in recession,'' John Ryding, chief U.S. economist at Bear Stearns Cos. in New York, said in a note to clients. ``We now put ourselves on recession watch.''