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Refugees at the Syrian Border. USHMM/Lucian Perkins.


To have a clear and accurate understanding of our assessments and analyses, please read these definitions to understand the terms used throughout the Early Warning Project website and reports.

Photo above: Refugees at the Syrian Border. USHMM/Lucian Perkins.


Types of Mass Atrocities

Mass Killing

The Early Warning Project’s Statistical Risk Assessment estimates the likelihood of a “mass killing” episode. We will consider a mass killing to have occurred when the deliberate actions of a specific armed group within a country—including but not limited to state security forces, rebel armies, and other militias—result in the deaths of at least 1,000 noncombatant civilians targeted as part of a specific group (in the same country), over a period of one year or less.

Deliberate Actions

This criterion distinguishes mass killing from deaths caused by natural disasters or infectious diseases, the accidental killing of civilians during war, or the unanticipated consequences of other government policies. Generally, fatalities are considered deliberate if they result from actions designed to compel or coerce civilian populations to change their behavior against their will, and if the perpetrators could have reasonably expected that these actions would result in widespread death among the affected populations. Examples of such actions include, but are not limited to, forced mass starvation, the intentional confiscation or destruction of healthcare supplies, forced relocation, and forced labor.

Noncombatant Civilian

A noncombatant civilian is any person who is not a current member of a formal or irregular military organization (e.g., militia, terrorist group) and who does not pose an immediate threat to the life, physical safety, or property of other people.

Specific Group

To distinguish “mass killing” from large numbers of unrelated civilian fatalities, the victims of mass killing must appear to be perceived by the perpetrators as belonging to a discrete group. That group may be defined communally (e.g., ethnicity or religion), politically (e.g., partisan affiliation or ideology), socio-economically (e.g., class or profession), or geographically (e.g., residents of specific villages or regions). Unrelated executions by police or other state agents would not qualify as mass killing, but capital punishment directed against members of a specific unarmed political or communal group would.


Most genocides are also mass killings, but many mass killings do not meet the legal definition of genocide. The term “genocide” has a very specific meaning under international law. (Because the legal definition of genocide relies on the intentions of the perpetrators, the Early Warning Project does not specifically forecast genocides.)

Under the 1948 UN Convention on the Prevention and Punishment of the Crime of Genocide, genocide means “any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:

  • (a) Killing members of the group;
  • (b) Causing serious bodily or mental harm to members of the group;
  • (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
  • (d) Imposing measures intended to prevent births within the group;
  • (e) Forcibly transferring children of the group to another group.”

Mass Atrocities

Mass atrocities are instances of “large-scale, systematic violence against civilian populations” (Straus, 40.) Although “mass atrocities” has no formal legal definition, it usually refers to genocide (as defined above), crimes against humanity, war crimes, and ethnic cleansing. Mass killing, as defined above, constitutes a subset of mass atrocities.

Crimes Against Humanity

Crimes Against Humanity are defined in the Rome Statute of the International Criminal Court as “any of the following acts when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack: murder, extermination, enslavement, deportation, imprisonment, torture, rape (and other gender-based or sex crimes), group-based persecution, enforced disappearance, apartheid, and “other inhumane acts of a similar character intentionally causing great suffering, or serious injury to body or to mental or physical health.”

War Crimes

War crimes are “serious violations of international humanitarian law,” (ICRC) i.e., theft, wanton destruction, murder, and ill-treatment. The Rome Statute lists some 50 separate instances of war crimes, including attacks on (a) civilian towns, (b) objects used for humanitarian assistance, or (c) any buildings that do not serve a military purpose (Straus, 38). War crimes are normally considered to be “mass atrocities” (and subject to jurisdiction of the International Criminal Court) “when committed as part of a plan or policy or as part of a large-scale commission of such crimes” (Rome Statute).

Ethnic Cleansing

Ethnic cleansing refers to the forced removal of an ethnic group from a territory. A United Nations Commission of Experts investigating the former Yugoslavia defined it as “rendering an area ethnically homogeneous by using force or intimidation to remove persons of given groups from the area." Though ethnic cleansing is not recognized as an independent crime under international law, the acts can constitute crimes against humanity, war crimes, and genocide.

Early Warning Project Terminology

Statistical Risk Assessment (SRA)

The Statistical Risk Assessment is an annual list produced by the Early Warning Project that ranks all countries with a population greater than 500,000 based on their likelihood of experiencing the start of a new mass killing episode. The assessment is based on publicly available data from a variety of sources, analyzed using a statistical model based on historical instances of mass killing. The results are published on our website and in yearly reports. All source data and the code for reproducing our analysis are available on GitHub, and CSV files of the data are available for download.

Learn more about our methodology

Public Opinion Pool

Our Public Opinion Pool draws on the “wisdom of the crowd” to provide real-time assessments of the likelihood of mass killing in more than a dozen countries of interest. Hosted on Good Judgment Open, a leading public forecasting platform, our Public Opinion Pool invites any interested individuals to register probabilistic judgments in response to questions about the likelihood of mass killing in selected countries. Forecasters are encouraged to regularly update their judgments to help us track changes in risk over time.

Learn more about our Public Opinion Pool

Comparison Survey

Each December, we conduct a survey on the relative likelihood of countries to experience the start of a mass killing episode in the following calendar year. This is our “Comparison Survey” (previously called “wiki survey”), since we use a “pairwise comparison” method: respondents choose between two countries, selecting the one they believe is more likely to experience a new mass killing. Results are visible in real-time on the hosting site,, and we publish a report on the results.

Learn more about our Comparison Survey

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from the Early Warning Project and the Simon-Skjodt Center for the Prevention of Genocide