00 = No second mother of this person in the household.
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 men. The person identified in MOMLOC2 will be the spouse or partner (SPLOC) of the person identified with MOMLOC.
The IPUMS family interrelationship variables address two types of ambiguity when forming links. First, we prioritize links based on how clear the relationship is between the two people being linked. Second, when links are not unique we use a series of logical steps to select between multiple potential parents. MOMRULE, POPRULE, MOM2RULE, and POP2RULE are all two digit variables that show how these two types of ambiguity were addressed when forming a parental link. The first digit indicates how direct the relationship is between the two people and the second digit indicates if the link was selected among multiple options and, if so, how it was selected.
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 householder is a direct link to the householder; the partner of the head will also be identified as the child's parent in this same step.
Parental rule value: 1-
- Child to Householder
- Child of Partner to Partner
- Householder to Parent
- Sibling to Parent
- Spouse to Parent-in-law
2nd level links
Parental rule value: 2-
- Grandchild to Child
- Child to Spouse, Partner
- Niece/Nephew to Sibling, Sibling-in-law
- Parent to Grandparent
3rd level links
Parental rule value: 3-
- Grandchild to Child-in-law
- Housemate to Housemate
- Roomer to Roomer
- Non-relative to Non-relative
- Other relative to Other relative, Aunt/Uncle, Niece/Nephew (for years 1969 to present)
- Unknown to Unknown
4th level links
Parental rule value: 4-
- Other relative to Child, Other relative (for years 1963 to 1968)
The allowed relationship links for determining a person's probable parent vary over time because of the level of detail collected regarding the relationship to the reference person. For example, in 1963 to 1986, there was no "Grandchild" option. In these early years, a child of the householder can be identified as the parent to an "other relative," although this is not allowed in more recent samples because there is more detail collected about the relationship to the reference person.
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.
As shown in the list below, parental links that are direct are made first, because these links are unique. For example, a person identified as the child of the householder will link directly to the householder. For those who were not linked to a parent through a direct link, the second step identifies people in households where there is one married couple who could be their parents. If there are multiple people who could pair to multiple married parents, they are split by age; for example, the eldest children will pair with the eldest couple. If there are no married couples that are possible parents, people who were previously married are selected as parents. If there are no parents who were previously married, the eldest single woman will be identified as the parent. The last potential parent who will be identified is a single man.
Clarity level 1
Parental rule value: -1
- This step identifies parents through links that are uniquely identified by relationship (direct links from previous list).
Clarity level 2
Parental rule value: -2
- When a person is in a household where there is one married couple who could be his/her parents. This couple is identified as the probable parents.
Clarity level 3
Parental rule value: -3
- When a person is in a household where there is are multiple married couples who could be his/her parents. Age is used to create pairings.
Clarity level 4
Parental rule value: -4
- When a person is in a household with no married couple who could be their parent, but there is only one potential unmarried parent in the household. This person is identified as their parent.
Clarity level 5
Parental rule value: -5
- When a person is in a household with no married couple who could be their parent and there are multiple possible parents. The first option selected is a woman who was previously married.
Clarity level 6
Parental rule value: -6
- When a person is in a household with no married couple who could be their parent, there is no previously married woman who would be their parent, and there are multiple possible parents. This step will identify a man who was previously married as the parent.
Clarity level 7
Parental rule value: -7
- When a person is in a household with no married couple or previously married people who could be their parent. In this step, the eldest single woman is selected as the parent.
Clarity level 8
Parental rule value: -8
- When a person is in a household with no married couple, previously married people, or single women who could be their parent. In this step, the eldest single man is selected as the parent.
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.
In 2016, the family interrelationship variables for all samples were revised to increase comparability across IPUMS projects and include same-sex couples. Many researchers who are familiar with the previous version of family interrelationship variables will find it useful to read a brief overview of the key differences of the New IPUMS Family Interrelationship Variables.
The pre-2016 version of MOMLOC, MOMRULE, and other IPUMS family interrelationship variables are available here.
Due to variation in the information available for linking fathers and children, there are some differences across years. For example, in prior to 1969, there was no "Grandchild" value on RELATE. In these samples, "Other relatives" under 22 are allowed to link to both "Other relatives" and to the "Child" as a mother when the age difference is appropriate.
Comparability with IPUMS-USA
The development of new family interrelationship variables was prompted by the desire to have more comparability between different IPUMS projects and over time. Each project has different allowed links because of different level of detail in each project, but the logic of assigning parents in ambiguous situations is the same.
- 1963-2018: All persons.
- No weights are available for this variable. Please refer to MOM2RULE for more information.