Charities' role in the Big Society
20 May 2011 Last updated at 23:35 BST
How valuable is the work carried out by charities and volunteer groups?
As the UK prime minister tries to encourage people to become part of what he calls the Big Society, researchers in the United States have attempted to work out the cash value of voluntary work in the community.
They have concluded that individual church charities carry out work worth millions of dollars - for free - every year.
The BBC's religious affairs correspondent Robert Pigott reports.