Volunteering in America: 2007 City Trends and Rankings

"Volunteering in America: 2007 City Trends and Rankings uses volunteer data collected by the U.S. Census Bureau and Bureau of Labor Statistics from 2004-2006. It ranks and includes profiles for 50 of the largest cities.."

Select by city or download the full report.

Portland Metro area profile

Portland. OR ranks 6th and on average, "had approximately 557,000
volunteers, who served 79.4 million hours per year between
2004 and 2006."