Schwab discloses their PFoF in their annual reports. It is 1.4% of their annual revenue. Page 31 of their 2018 10-k or, if you want a search string, Ctrl-F for

Schwab discloses their PFoF in their annual reports. It is 1.4% of their annual revenue. Page 31 of their 2018 10-k or, if you want a search string, Ctrl-F for "Order flow revenue was $139 million during 2018, $114 million for 2017, and $103 million in 2016. "