hypothesis is that individuals can anticipate their behavior in high-empathy "hot states", while in low-empathy "cold states". While this model assumes a high degree of sophistication on the part of the individual, research by Andreoni, Rao, and Trachtman explores this very phenomenon by observing avoidance and donation behavior of customers entering a supermarket during the holidays. Customers often walked to a further entrance to avoid solicitors for the Salvation Army. According to their model, "empathetically vulnerable" individuals who are not able to give (for budgetary reasons), faced the greatest incentive to avoid collectors because of the guilt they would experience upon saying "no". Grouping behaviors Charities may strategically employ categorical donor recognition. For example, a charitable organization may distinguish any gift between $500-$999.99 by a title distinct from that awarded for gifts above $1,000. As a consequence, the social signaling component of the warm-glow effect (in extrinsic operationalizations of warm glow) suggests individuals should be motivated to make the minimum donation to acquire their desired categorical status. Consistent with this hypothesis, research has indicated significant grouping behavior of donors around category minimums. Inefficiency in charitable allocation A majority of those who choose to give some portion of their wealth to charity support multiple different causes. Rather than giving 100% of their cumulative donations to the same source, there exists a widespread preference to distribute funds across charities. The warm glow model explains this by recognizing that givers receive multiple warm glows through giving to multiple causes, thus supporting the preference to make multiple small contributions. As a consequence, some scholars suggest an efficiency loss due to high volumes of small donations – which are less efficient to process — rather than fewer large donations. Moral philosopher Peter Singer mentions warm-glow givers in his 2015 book, The Most Good You Can Do. Singer states that these types of donors "give small amounts to many charities [and] are not so interested in whether what they are doing helps others." He references "empathetic concern" and "personal distress" as two distinct components of warm-glow givers. Inefficiency in charitable selection Warm glow may offer an explanation for some of the observed inefficiencies in charitable giving. For example, United States citizens directed more than 60% of their total charitable contributions to religious groups, education institutions, art organizations, and foundations in 2017; compared to under 7% in foreign aid. According to models of social justice and economic