San Francisco ? Americans needed more emergency food and shelter last year than the year before, according to a 24-city survey released Monday by the U.S. Conference of Mayors.

Requests for food assistance grew by 12 percent overall during the past year, with 76 percent of the cities surveyed reporting an increase. Appeals for shelter assistance increased by 6 percent, with 71 percent of cities showing an increase, according to the annual Hunger and Homelessness Survey.

“The statistics continue to get worse and worse in spite of our Herculean efforts,” said San Francisco Mayor Gavin Newsom, who, with Mayor Paul Pate of Cedar Rapids, Iowa, co-chairs the conference’s Task Force on Hunger and Homelessness.

Among the survey’s findings:

¢ On average, 18 percent of requests for emergency food and 14 percent of requests for emergency shelter were estimated to have gone unmet during the last year.

¢ Eighty-seven percent of cities said the average length of time that people were homeless – seven months – increased during the past year.

¢ Lack of affordable housing topped the list of causes of homelessness. Low-paying jobs, mental illness, substance abuse and other things also were factors.

¢ Fifty-four percent of those who asked for emergency food were families, children and their parents. Forty percent of adults requesting food were employed.

Officials said evacuees from Hurricanes Katrina and Rita have not caused a significant strain on resources, but warned the impact might be felt next year.

The data were collected during November and December for the period of Nov. 1, 2004 to Oct. 31, 2005, from city officials, community-based providers and government agencies.