Appendices - 3
Appendix B: Coding of FBI Murder Data
Our data on homicide come from the FBI Uniform Crime Reports (UCR).
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The UCR data are derived
using a voluntary police agency-based reporting system. The Supplementary Homicide Reports of the UCR
provide incident-level information on criminal homicides, including data describing the date and location of the
incident, and a range of information on both the offender and the victim. This data codes the relationship of the
victim to the murderer, where known. We would like to be able to look exclusively at murders that may be
affected by unilateral divorce. Therefore we are looking for cases in which the perpetrator maybe motivated by
the laws pertaining to divorce – intimate homicides. A useful definition of the treatment group should include
intimates such as spouses, ex-spouses, other partners, and other family members. However, relationships such as
common-law spouse, boyfriend/girlfriend, and even ex-spouse are not consistently coded through our sample.
While time-fixed effects will effectively difference out inconsistencies that are common across states, we are
worried that family law reform may have changed the common meanings of certain definitions of the treatment
group. (For instance the distinction between marriage, common-law marriage and live-in partners has changed
with the social meaning of these terms, which has in turn been affected by family law.
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) As such we can think
of a bias/efficiency tradeoff. The most efficient strategy is based on a narrow definition of intimate homicide
that includes only spouses, but runs the risk that this category is not well-defined through the sample period. At
the other extreme, perhaps the safest identification strategy is to assume that the legal regime did not affect
murder between strangers, but did affect murder where the victim is known to the murderer – in any capacity.
We employ three definitions of the treatment group – ranging from that which we are most interested in (spousal
murder) to definitions which are less likely to suffer from coding-induced biases (stranger/non-stranger). The
definitions used are outlined in the following table.
Alternative definitions of the “Treatment Group”
Classification Treatment group Control group
Spouses
1968-72
“Spouse kills spouse” All other*
1972-75
“Spouse kills spouse” All other*
1976-94
“Husband”, “Wife”, “Common-law Husband”, “Common-law
Wife”
All other*
Family
1968-72
“Spouse kills spouse”, “Parent kills child”, “Child kills parent”,
“Other family situation”, “Love Triangle”
All other*
1972-75
“Spouse kills spouse”, “Parent kills child”, “Child kills parent”,
“Relative kills relative”, “Other family situation”, “Love
Triangle”
All other*
1976-94
“Husband”, “Wife”, “Common-law Husband”, “Common-law
Wife”, “Mother”, “Father”, “Son”, “Daughter”, “Brother”,
“Sister”, “In-law”, “Stepfather”, “Stepmother”, “Stepson”,
“Stepdaughter”, “Other family”, “Boyfriend”, “Girlfriend”,
“Ex-husband”, “Ex-wife”, “Homosexual relationship”
All other*
Known
1968-72
“Spouse kills spouse”, “Parent kills child”, “Child kills parent”,
“Other family situation”, “Love triangle”, “Money”, “Revenge”,
“Other argument”
All other*
1972-75
“Spouse kills spouse”, “Parent kills child”, “Child kills parent”,
“Relative kills relative”, “Other family situation”, “Love
Triangle”, “Argument/money”, “Other arguments”
All other*
1976-94
All other “Stranger”, “Unknown
Relationship”
* Note that “All other” includes “Murder reason unknown”, “Not stated”, “Not coded” and “Unknown relationship”.
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Data for 1968-75 are from ICPSR Study No. 8676, “American Homicide, 1968-1978: Victim-Level Supplementary
Homicide Reports”, Marc Riedel and Margaret Zahn (1994). Data for 1976-94 are extracted from ICPSR Study No.
6754, “Uniform Crime Reports [United States]: Supplementary Homicide Reports, 1976-1994”, James Alan Fox
(1996). The consistency of these data is discussed in Appendix B.
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An additional problem is that we cannot infer that the share of murderer-victim relationships that are coded are
representative of those for which no code was recorded.