The phrase "to know every contributor" means to be aware of and familiar with all the people who have made contributions or participated in a certain activity or project. Full definition
The biggest known contributor to autism risk is having a family member with it. (scientificamerican.com)
The media is a well known contributor for attacking clubs to scrutinise them at every possible opportunity, especially the big clubs of the country. (justarsenal.com)
One of the most prominent funders is the Knowledge and Progress Fund, a Charles Koch - run organization and one of the group's largest known contributors, having donated nearly $ 9 million from 2005 to 2012. (sourcewatch.org)