WASHINGTON (AP) -- Unemployment rates rose in more than 90 percent of U.S. cities in June, mirroring a national slowdown in hiring.The Labor Department said Wednesday that unemployment rates rose in 345 large metro areas. They dropped in 20 cities and were unchanged in seven. That's worse than May, when rates rose in only 210 cities. And it is a sharp reversal from April, when unemployment rates fell in nearly all metro areas.The biggest increase was in Joplin, Mo, which was hit by a major tornado on May 22. The city lost 9,400 jobs in June, and the unemployment rate jumped nearly 2 percentage points, to 9.6 percent.The national unemployment rate ticked up to 9.2 percent in June, the highest level this year.Businesses have cut back on hiring this spring. Employers added only 18,000 jobs in June, the fewest in nine months. That's down sharply from an average of 215,000 net job gains each month in the February-April period.Economic growth declined to less than 1 percent in the first half of this year. That's slowest pace since the recession ended two years ago.Stagnant wages and high gas prices have cut into consumer spending, which accounts for 70 percent of economic activity. Spending fell in June for the first time in 20 months, the government said Tuesday.Unemployment rose in many college towns, likely because academic activity wound down for the summer. Unlike the national data, the metro unemployment data isn't adjusted for seasonal factors.Champaign-Urbana, Ill., the home of the University of Illinois, reported the second-largest increase. The metro area's unemployment rate rose from 6.9 percent in May to 8.6 percent in June. College towns in Texas, New Mexico, and Arizona reported similar jumps.Twelve cities reported unemployment rates greater than 15 percent. Eleven of those cities were in California. El Centro, Calif., had the nation's highest rate at 28.5 percent. It was followed by Yuma, Ariz., at 26.9 percent. Both cities are big agricultural producers and depend heavily on migrant farm work.Bismarck, N.D. had the nation's lowest rate, at 3.6 percent. It was followed by Lincoln, Neb. at 4.1 percent, and Fargo, N.D. at 4.2 percent.