-10 percent

Amid all the commonly stated benefits of membership in associations, often overlooked are the potential benefits to a person's well-being. A new study on health in retirees conducted by the University of Queensland in Australia found that, for every group membership a person dropped in the first year of retirement, his or her reported quality of life six years later was 10 percent lower—a correlation "comparable in size to those associated with physical activity," the researchers noted.

Source: British Medical Journal, February 2016

[This article was originally published in the Associations Now print edition, titled "Group Vitality."]