There is a difficulty in measuring this as the greater amount of relevant research focuses on violence perptrated by one partner (usally male) to the other (usually female). There is less empirical data with regard to coercive and controlling behaviour or other forms of maltreatment of intimate partners.
A notable finding however is that mild and severe violence to women was accompanied by threats to do greater harm to the women, such as sexual assaults and acts of coercin. The children of these abused women were potentially exposed to different forms of psychological maltreatment several times a week, in addition to frequent mild and severe violence.
It is therefore sensible to understand violence as existing along a continuum and the less severe forms of maltreatment can be as harmful as severe forms of violence if repeated often enough. In assessing risk to the child from exposure to violence and abusive behaviour, the assessor needs to include in their inquiry a range of abusive behaviours, not just overt physical violence but also frequency of the behaviours and whether the abusive or violent acts are experienced by the child directly or indirectly (whether they see it, hear it or just know about it).