In 2000, the MacArthur Foundation began the Window of Opportunity initiative, a 20-year, $187 million project intended to help preserve privately owned affordable rental housing. The authors of this report assess whether the initiative achieved its goals and identify lessons learned about effective preservation practices. In doing so, they also provide a summary of the evolution of practices in preserving affordable rental housing, discuss challenges and opportunities for preservation going forward, and identify lessons learned that may help other philanthropies in their own philanthropic initiatives, even if they do not pertain to housing.

The authors find that the MacArthur Foundation met most of its goals for Window of Opportunity. As the initiative nears its end, large nonprofit preservation developers/owners have greater financial capacity and reputation, there are more resources and vehicles for preservation, and, to a lesser degree, the policy environment has changed to the benefit of preservation. However, Window of Opportunity has not achieved its most ambitious federal policy goals and is likely to fall short of its target for the number of privately owned affordable rental housing that will be preserved.