A majority of American cities participating in a recent survey have seen an increase in the number of requests for emergency food assistance, the U.S. Conference of Mayors reports. The Washington-based conference, in its annual Hunger and Homelessness Survey, said in mid-December that 16 of the 19 cities that responded to questions about hunger saw increases in requests for emergency food aid in the last year. In addition, an average of 17 percent of people seeking food assistance are not receiving it. Nineteen of 23 cities in the analysis expect requests for food assistance to increase this year. The lack of affordable housing was the most common cause of homelessness for households with children. Other causes included poverty and domestic violence. For single individuals, mental illness and substance abuse were among the most common causes.