Oregon Revised Statutes Insurance § 746.150

(1) For property, inland marine, casualty or surety insurance, an insurer may combine for dividend purposes the experience of a group of persons or risks any of which are within this state, except for workers' compensation insurance done in compliance with ORS 746.145 and subject to rules adopted by the Director of the Department of Consumer and Business Services.

(2) The director shall make reasonable rules regarding such dividend groupings as an aid to the effectuation and enforcement of the Insurance Code. Such rules shall have as their purpose the prevention of misrepresentation, unfair discrimination and other unfair trade practices, and may among other things require that:

(3) An insurer shall not unfairly discriminate in the allocation of dividends among the participants in such a dividend grouping.

(4) The system for allocation of dividends among the participants may provide for allocation at a fixed percentage of premiums, or may provide for variations in the percentage of premiums paid as dividends, or may provide for other variations in determining the amounts of dividends allocated to participants. The variations may be based on loss or expense factors or on other reasonable considerations, such as risk size, risk location or industry or trade hazard classification, that have a probable effect on losses or expenses.

(5) Failure to apply in a consistent manner the dividend allocation system specified in an insurer's dividend declaration shall be prima facie evidence of unfair discrimination.