Mother Teresa, who would have turned 100 this week, helped spark a new missionary model which increasingly sees ordinary people volunteer while on vacation. "Voluntourism" attracts some questions — over the sustainability of and what can be accomplished in shorter-term mission work abroad — but "proponents point out that it often leads to more substantial volunteerism and has cross-cultural benefits." "A 2008 poll by the University of California at San Diego found 40 percent of Americans willing to spend several weeks on vacations that involve volunteer service, and 13 percent willing to spend an entire year."