Collective Philanthropy: Describing and Modeling the Ecology of Giving [pdf] [PLOS One]

William L Gottesman, Andrew James Reagan, Peter Sheridan Dodds


Annual donations to a charitable organization tend to follow a power-law size distribution specific to that organization's purpose. Organizations may be able to use this information to help plan future campaigns.


Reflective of income and wealth distributions, philanthropic gifting appears to follow an approximate power-law size distribution as measured by the size of gifts received by individual institutions. We explore the ecology of gifting by analysing data sets of individual gifts for a diverse group of institutions dedicated to education, medicine, art, public support, and religion. We find that the detailed forms of gift-size distributions differ across but are relatively constant within charity categories. We construct a model for how a donor's income affects their giving preferences in different charity categories, offering a mechanistic explanation for variations in institutional gift-size distributions. We discuss how knowledge of gift-sized distributions may be used to assess an institution's gift-giving profile, to help set fundraising goals, and to design an institution-specific giving pyramid.


  • We present data showing the size of gifts received by charitable organizations tend to follow a heavy tailed distribution consistent with a power-law size relation.
  • Gifts received by charitable organizations follow a size distribution distinctly related to that organization's purpose.
  • Individuals at different income levels apply different preferences when selecting their charities.
  • The size of gifts sought in an annual campaign can be anticipated both by an organization's purpose and by its prior gift history.
  • We construct a model of philanthropic giving that accounts for different power law exponents for different categories of charitable institutions.
  • An institution may be able to use this model in annual and capital campaigns to construct a giving pyramid specific to that institution.