Using the number "Domestic Violence-Related Calls for Assistance" as reference on how to scale from Kentucky to California, ~60 % of divorce cases will have no mention of violence.
(In 2004 Kentucky had 800 calls per 100 000 inhabitants and California had 500; the assumption is that number of allegations in hearings scale with the calls of assistance).
https://aifs.gov.au/publications/allegations-family-violence...
https://oag.ca.gov/crime/cjsc/stats/domestic-violence
http://www.ncdsv.org/fortcampbell/I-12_Kentucky%20DV%20Facts...
http://www.census.gov/popest/data/state/totals/2004/tables/N...