I am often asked this simple question. While easy answers are convenient, well-researched and complex ones are more valuable. Matthew Gardner (http://gardnereconomics.com/) gives a well-considered, humorously-delivered answer. I am hosting a table on Tuesday March 27th and again (same content) Thursday March 29th for friends who would like to attend. Both events are at the Center for Urban Horticulture at UW from 5:45pm-7:15. I am confident this will be worth it and hope to hear from you.