Explaining the curve in the U-shaped curve

In a previous paper we have demonstrated that for the total population of households, including non-givers, lower income households participate less and donate smaller average percentages of their household incomes than do higher income households. In this paper we inquire about the relative generosity of that sub-population of households that actually donate to charitable causes. We base our analysis on data collected in the 1990 national survey of Giving and Volunteering in the United States conducted by the Gallup Organization for Independent Sector. In the first section we review the factors that differentiate the upward sloping curve describing the population of all households and the U-shaped curve describing the sub-population of contributing households. In the second section we demonstrate that a substantial proportion of the curvature in the U-shaped relationship operates through giving to religion. In the third section we show that giving by the 7 per cent of high givers increases the curvature while the giving by the 93 per cent of normal givers attenuates the curvature. In the fourth section we combine the previous two analyses by looking at the patterns of religious and non-religious giving for both normal and high givers. We conclude that income is not a reliable indicator of who is generous or selfish in regard to philanthropic giving. An earlier version of this paper was prepared for Presentation at the Annual Conference of the Association for Research on Nonprofit Organizations and Voluntary Action, New Haven, October/November 1992. The authors are grateful to the T.B. Murphy Foundation Charitable Trust, the Lilly Endowment, and the Indiana University Center on Philanthropy for their support of this research. We are also grateful to Virginia A. Hodgkinson and Stephen M. Noga for providing Independent Sector survey data and for sharing their technical expertise.