Ames’ 1.5 percent unemployment rate was the lowest among U.S. metro areas in May, continuing the Story County university town’s run as one of the toughest places to find workers. Yuma, Ariz., had the highest rate, at 16 percent. Jobless rates were below the national figure of 3.6 percent in 191 metro areas, and 175 areas were above that rate. Another 22 equaled the national unemployment rate. Unemployment rates were lower in May than a year earlier in 350 of the 388 metro areas, higher in 20 areas, and unchanged in 18 areas, the U.S. Bureau of Labor Statistics reported.