I've seen & heard that percentage figure internally, especially as it's increased over the past decade. But I can't seem to find it in 10minutes of searching public documents.

Aside from donating time and money, the company's service is also seen as a fundamental piece of the global economy today. Providing a common baseline of financial data and price transparency of assets creates liquidity and helps keep asset prices low. It also allows smaller players to enter the financial services industry without needing to be in the "Old Boys' Club". It also helps developing countries and other emerging markets to list their sovereign debt and manage investors.

1: https://www.bloomberg.org/