I don't know. I think the 'MoralityWeight' tag is for that. Personally, i think the attribute tags specify the result (as in adding research/manufacturing/etc) because there is no other tag that specifies this. It isn't the 'type' tag like it is with anomalies because there are only two types; one for newly colonized worlds and one for already colonized worlds.
And as i browsed through the events.xml file, every time the bonuses were all +/- research bonus for example, all attributes were the same value. That while when the bonus/penalties were different for each option, the values were different as well. If this is true, it's just a matter of crossreferencing the original events to get the correct values.
