If filtering is applied to the current field, the ShowNewValues property specifies whether new field values (values that have been added to the datasource after the filter condition was set) are shown or hidden by default.
If filtering is not applied to the field, new field values are always displayed, regardless of the ShowNewValues property value.
The ShowNewValues property is also not in effect if the current field is a part of a field group that uses a hierarchical filter (see PivotGridControl.GroupFilterMode). In this instance, use the group's PivotGridGroup.ShowNewValues property.