Unemployment rates fell in roughly two-thirds of U.S. cities last month, despite zero job growth nationwide.

The Labor Department said Wednesday that unemployment rates dropped in 237 of the nation's largest metro areas in August from July. They rose in 103 and stayed the same in 32. That's an improvement from July, when rates fell in 193 areas and rose in 118.

Some areas with large agricultural sectors added jobs to coincide with the start of the harvest. Auto companies boosted hiring in several other cities.

Rates also fell in Jackson, Miss., and other cities because thousands of people gave up looking for work. People who are no longer searching for jobs aren't counted as unemployed.

Unlike national and state data, metro unemployment figures are not adjusted for seasonal changes.

The U.S. economy added no net jobs in August, the least amount of hiring in almost a year. The national unemployment rate remained 9.1 percent for the second straight month.

Businesses pulled back on hiring this summer after the government said the economy barely expanded in the first six months of the year.

Most of the cities that reported sharp improvement still suffer from steep unemployment rates. Unemployment dropped the most last month in Yuba City, Calif., a heavily agricultural area in Northern California. The city's rate fell from 18.6 percent in July to 17 percent last month.

Another big decline was in Modesto, Calif., home of the E. & J. Gallo Winery, the largest winemaker in the world. The rate there dropped from 17.3 percent in July to 16 percent last month.

The unemployment rate in Mansfield, Ohio fell from 11.4 percent to 10.1 percent, mostly because the city added manufacturing jobs.

El Centro, Calif. and Yuma, Ariz. had the highest unemployment rates among cities, at 32.4 percent and 29.4 percent, respectively. They are adjacent counties with heavy farm economies and large contingents of migrant labor. Yuma's rate fell while El Centro's ticked up.

Bismarck, N.D. reported the nation's lowest unemployment rate, at 3 percent. Lincoln, Neb. had the next lowest rate, at 3.6 percent, followed by Fargo, N.D., at 3.9 percent.

Among the 49 cities with populations of 1 million or more, Las Vegas had the highest unemployment rate, at 14.2 percent. Riverside-San Bernardino, Calif. had the second highest, 14.1 percent. Both were hit by huge housing bubbles and haven't yet recovered.

Oklahoma City, Okla. had the lowest rate among big cities, at 5 percent.