The Philanthropy Outlook was developed using well-established econometric methods. The models selected for producing each component of The Philanthropy Outlook are composed of a linear combination of growth rates (or 1-year differences) for key indicators. The results point toward linkages between specific economic variables and philanthropic giving. These linkages can be positive or negative (inverse), as well as direct or indirect. With these results, we cannot say that a particular variable caused philanthropy to rise or fall; rather, they point us toward what is likely to happen and why.
The Philanthropy Outlook is meant to be informational. The Indiana University Lilly Family School of Philanthropy and Marts & Lundy make no guarantees about its accuracy. Similar to other types of predictions, it is impossible to know ahead of time all the factors that will affect giving into the future. While The Philanthropy Outlook is based on scientific methodology, there are limits to the use of such methodology to predict future outcomes.
We have confidence in the measures we have taken to adjust for the Tax Cuts and Jobs Act (TCJA), including our ongoing data partnership with the University Of Pennsylvania Wharton School Of Business and the incorporation of key variables directly affected by TCJA in the models. However, the sweeping changes ushered in by TCJA represent an out-of-sample change, with possible behavioral effects that are difficult to estimate before final data has been received.