MOM2RULE is a constructed variable that indicates the method by which the probable child-mother link shown in MOMLOC2 was identified. MOMLOC2 is only non-zero when the parents identified for a person are both women. The person identified in MOMLOC2 will be the spouse or partner (SPLOC) of the person identified with MOMLOC.
We first prioritize links within a household based how clear the relationship is between the two people being linked (using RELATE). The links in the first priority level are direct links, so there are no age restrictions placed on these links. For links in the second priority level, the difference in the age of the "child" half of the link the "parent" half of the link must be 15 to 44 for mothers and 15 to 60 for fathers. For links in the third through fifth level, the same age difference restrictions apply. In addition, third- through fifth-level links only occur when the "child" half of the link is under 22 and is single. The spouse or partner of someone's parent will be identified as their parent in the same step. For example, the child of the head is a direct link; the partner of the head will also be identified as the child's parent.
While the first step to finding a spouse or parental link is based on their relationship to the reference person, this may not enough to uniquely determine the link. It is not uncommon for a person to be in a household where there are multiple people who could be their parent. To be able to select among multiple potential links, we apply a set of logical steps within each priority level that selects among multiple potential links. This information is captured in the second digit of MOM2RULE.
The two steps together determine the value of MOM2RULE. For example, in a household consisting of a female householder, a female unmarried partner, and a child, the householder will be identified as the child's first mother with MOMLOC and the partner will be identified with MOMLOC2. Both links happens with priority 1 during clarity level 1. MOMRULE and MOM2RULE would therefore be 11.