Unpacking the Unlikely Origins of a Major Gift Fundraising Benchmark

My unexpectedly detailed research into the origins of an industry best practice guideline for portfolio sizes came from a simple request from my principal and major gift (PMG) team’s vice president (VP). As a prospect management professional, I had concerns about the capacity of our frontline team to manage the growing number of prospects within our PMG donor portfolios, which I shared with our new VP. In response, she asked, “Can you gather some industry guidelines on portfolio size that show ours have exceeded the accepted capacity?” I knew I wouldn’t be able to do that. Because I knew the common industry benchmark for a “maximum” PMG portfolio size (150), and I knew our portfolios did not exceed it. But I also knew that didn’t mean our portfolios were of a manageable size for our frontline team members. Instead, I began research to unpack the origins of that guideline.  I wanted to find evidence to help support my argument that the industry benchmark was likely not relevant to our PMG program.

The most often cited industry guideline for the maximum size of a major gift portfolio, and the number I had in my head when I received the above request is 150, as noted above. As I researched various guidelines, I confirmed that there is no one industry best practice guide and portfolio size recommendations range based on a single source. Despite this,150 is generally considered the absolute maximum portfolio size industry professionals recommend.

So where does this number come from? Its origins appear to be the work of British anthropologist Robin Dunbar.^1,2 In the 1990s, Dunbar proposed in his research on the social relationships of primates that the cognitive limit on the number of people with whom a single person can maintain stable interpersonal relationships was about 150. This conclusion came from analyzing the brain sizes of non-human primates and comparing this to the size of that species' social groups, determining there was a correlation between the two, and applying that formula to the size of the human brain.³

This theory was popularized and applied to a variety of other disciplines, eventually making its way to business management⁴ — the likely path that brought it to major gift fundraising. While there has been subsequent criticism of Dunbar's research and his methods calling his conclusions into question, there are clear reasons for us to question if Dunbar’s research is in fact relevant at all to portfolio management. 

“Dunbar’s Number” is not a concept developed in the context of professional relationships — it considers a person’s whole social capacity. Which would mean a fundraising professional could then, in theory, only carry a portfolio of 150 donors if those donor relationships represented all the relationships in their life with no other connections such as friends, family or co-workers. To accurately apply the theory behind Dunbar’s Number to portfolio sizes, one would need to subtract the number of personal relationships the major gift officer has from the150, which would leave that fundraiser’s “capacity” for professional donor relationships drastically minimized — a deeply impractical notion.

Additionally, Dunbar’s number is a calculation based on cognitive capacity, not time management. Just because this research proposes a person has the cognitive ability to manage 150 stable individual relationships, that does not mean a fundraiser has enough working hours to maintain 150 meaningful donor relationships successfully. Think about all the things you have the cognitive ability to do: learn other languages, read countless books, construct a model of the Taj Mahal from toothpicks. You can’t accomplish any of these things without the time in your day to do them.

More abstractly, it's also worth questioning if Dunbar’s definition of a stable interpersonal relationship is truly applicable to a successful donor relationship. Dunbar has described the level of relationship referenced in Dunbar’s Number as “the number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar.”⁵  Is that a relationship dynamic relevant to donors and fundraisers? 

While it seems clear that its origin has little relevance to fundraising, I acknowledge that since Dunbar’s Number has been in the ether of our industry, having a number, any number, authoritatively recognized as a “maximum” portfolio size has offered benefits, despite its anthropological foundation. Dunbar’s Number has meant we as industry professionals have had something clear and specific to point to, with the heirs of legitimate research behind it, to persuade leadership that there is scientific proof that ballooning portfolios of 300+ donors are unmanageable for staff and limit their fundraising success. The widely-accepted number of 150 will likely continue to be a helpful guiding benchmark for organizations trying to change an internal culture where portfolios of hundreds of donors are standard. But as prospect development analysis evolves and becomes more strategic and sophisticated, it's time to decouple our industry from a benchmark we know stems from research on primates and is irrelevant to our work.

If 150 isn’t the right maximum PMG portfolio size, what is? The answer is unfortunately not simple, or a static number. The right portfolio size will be different for every organization, and even vary from one frontline fundraiser to another within the same organization. It will depend on a number of factors and variables unique to your program and staff. Part two of this article will share experiences of prospect development professionals with portfolio size analysis and explore considerations to help determine the right major gift portfolio size for your team.

References

1. https://archetypeconsulting.com/blog/how-to-organize-and-measure-major-gift-performance#:~:text=The%20ideal%20portfolio%20size%20is,person%20can%20maintain%20stable%20relationships.%E2%80%9D
2. https://www.linkedin.com/pulse/fundraisers-can-use-dunbars-theory-guide-major-gift-hutchinson/
3. https://www.sciencedirect.com/science/article/abs/pii/004724849290081J?via%3Dihub
4. https://www.cultivatedmanagement.com/the-rule-of-150/#:~:text=The%20Rule%20of%20150%2C%20or,connections%20between%20people%20and%20teams
5. Dunbar, Robin (1998). Grooming, gossip, and the evolution of language (1st Harvard University Press paperback ed.). Cambridge, Massachusetts: Harvard University Press. p. 77. 

Juliet Carpenter
Director of Prospect Management and Strategy, Planned Parenthood Federation of America

Juliet Carpenter is a prospect development professional with over 15 years of experience in non-profit fundraising. She began her development career as an Americorps VISTA member in Kansas City, and has contributed to organizations that support food access, the arts, higher education, the environment and reproductive healthcare through her work. She currently serves as the director of prospect management and strategy for Planned Parenthood Federation of America.