It seems like “deeply committed” is doing a lot of work there. In the last EA survey, it seemed like the median donation from a person who identified as “EA”, listed “earning to give” as their career, was not a student, and believed they should give now rather than give later was $1933. At typical starting software engineer salaries (which I would guess is a typical career for a median “earning to give” EA), this represents a 1-5% donation. This suggests the pledge would increase the donations of over 50% of EAs who list their primary career path as earning to give (so the argument that the mental effort needed to keep the pledge would distract from their careers doesn’t apply). Link to analysis here: https://www.facebook.com/bshlgrs/posts/10208520740630756?match=YnVjayBzaGxlZ2VyaXMsc2hsZWdlcmlzLHN1cnZleSxidWNr
Edit: Speaking for myself only, not my employer.
Some kind of anonymous survey mechanism that managed to capture people who had interacted with EA in a low-to-medium-intensity way (eg, through the Facebook group or one of the websites, through playing a giving game at a campus group, attending one meet up of a campus group, etc) and tracked a) whether they interacted at higher-intensity (eg, applying to EAG) later, and b) whether they internally felt it was welcoming.