I read a little of a journal article about older volunteers in the USA.

The article is

Tang, Fengyan. "Socioeconomic Disparities in Voluntary Organization Involvement Among Older Adults" Nonprofit and Voluntary Sector Quarterly, 37, 1, March 2008.

This paper describes a statistical modeling of data from the Americans Changing Lives (ACL) survey from the Survey Research Center of the University of Michigan. The author investigates the effects of socioeconomic status on type and scope of volunteering of older adults. The author concludes that education alone not income has a positive effect on types and scope of volunteering. The author calls on voluntary organizations to help older adults with less education volunteer and thus reduce disparities caused by inequalities in society.