For-profit companies have a market capitalization equal to the number of shares times the price. Non-profits however do not issue equity. However, market capitalization is an important concept. Especially, since most indexed portfolios are market-cap weighted. Market-cap weighting means that when you buy into a total market index you are buying more of the largest, most established companies and less of the more risky startups. Non-profit indexes would benefit from this as well, since we would want to naturally contribute more money to organizations that have a proven track record of efficiency and getting results attacking the most pressing global causes.
So, for non-profits it may be better to consider the concept of a “Success Cap”. This could be measured by the amount of funds successfully deployed to past projects. Thereby an established non-profit should have a larger “Success capitalization” than an unproven company raising funds and carry more weight in indexed portfolios. This also creates a motive for less established players to become more efficient at raising and deploying funds.