Eighteen graphs about the death penalty

A guest post by Matt Sundquist, Founder of Plot.ly

This post details how, where, and when the death penalty has been applied in the United States. We’ll examine opposition to the death penalty (9 graphs), the deterrence argument (5 graphs), and trends in the death penalty and public opinion (4 graphs).

We used Plotly’s APIs for Python, MATLAB, and R to make these graphs. We used import.io’s Plotly integration to access and share data from the Death Penalty Information Center.

Part 1: Opposition To The Death Penalty

The death penalty is left up to and applied by states. For a visual representation of the geographical applications, study the map below made with Python. Texas executes more people than any other state. Hover your mouse to see data.

Executions by U.S. State Since 1819

This bar chart breaks down the same data and shows the number of executions in each state. One report showed that 2% of counties in the U.S. have been responsible for the majority of cases leading to executions since 1976.

Executions by State

The graph below summarizes the history of executions in the U.S. The gap occurred when the Supreme Court suspended the punishment for a few years, concluding that it was imposed “wantonly” and “freakishly.” The Justices weighed whether it violates the Eighth Amendment’s ban on cruel and unusual punishment.

Executions by Method


Growing Length of Time Between Sentencing and Execution

Opponents of the penalty argue that it is cruel to have inmates on death row for decades. As of 2014, there were 3,002 inmates on death row in the U.S. This line chart shows the trend with a line of best fit.

Executions by Method


In 1990, the U.S. General Accounting Office concluded that “the victim’s race influenced the likelihood of the defendant being charged with capital murder or receiving the death penalty.”

<br>Race of Victims in Death Penalty Cases

A black defendant accused of murdering a white victim is more likely to receive the death penalty than a white defendant accused of murdering a black victim.

<br>Executions for Interracial Murders


A study on the death penalty in California concluded that:

“a combination of high trial costs, a lengthy appeals process, and incarceration costs for the more than 700 inmates on California’s death row have caused the state to spend well over $4 billion on the death penalty since its reinstatement in 1978.”

<br>Money Spent on California Death Penalty


Failed Executions and Innonence

Lethal injection is the most popular method in use (recall our first graph). It is also the most risky. More recent periods have been the worst; between 1980 and 2010, 8.53 percent of executions were botched in some way.

<br>Percent of Botched Executions, 1900 to 2010

DNA analysis and new forensic techniques can exonerate prisoners. The National Registry of Exonerations lists 106 who were sentenced to death who have been exonerated since 1989.

<b>Exonerations from Death Row</b><br><br><i>Number of Prisoners Sentenced to Death Who Were Later Cleared</i>,<br><i>by Year of Exoneration</i>


Part 2: The Deterrence Argument

Some supporters of the death penalty argue that the penalty discourages murderers. The Wall Street Journal published a version of the plot below and wrote an article along these lines:

…[O]ur recent research shows that each execution carried out is correlated with about 74 fewer murders the following year.


<br>Relationship Between Execution and Murder

The plot seems convincing. But violent crime overall has diminished in the past two decades. This is a broad trend. Remember that correlation does not imply causation.

<br><b>Violent Crime in the United States</b>

And despite different approaches to the death penalty, homicide rates in the U.S. and Canada are similar. Presumably factors besides the death penalty contribute to homicide rates. <br>Homicide Rates and the Death Penalty in the U.S. and Canada

Homicide rates are higher in death penalty states than non-death penalty states.

Murder Rates in Death & Non-Death Penalty States<br>and the Percent Difference

Examining the data at a state level–as one researcher did for 1998 data–also does not demonstrate a deterrance effect.

Homicide Rates in Death Penalty and Non-Death<br>Penalty States in 1998

Part 3: Trends in the Death Penalty

The United States is the only country in the G7 (major advanced economy) to still execute people. From figures in 2013, the U.S. ranks sixth in the world for the use of capital punishment behind China, North Korea, Iran, Iraq, and Saudia Arabia. The United Nations General Assembly has adopted resolutions calling for a global moratorium on executions. China, India, the United States, and Indonesia have consistently voted against the resolutions.

Number of Countries That...

The number of inmates sentenced to death increased between 1980 and 2010.

Number of U.S. Inmates Sentenced

Public Opinion

The Gallop Poll Social Series on Crime tracks public opinion on the death penalty. The data below was gathered from a random sample of 1,028 adults. The margin of error is ±4 percentage points, indicated by the error bars on the plot.

Are You in Favor of the Death Penalty?

Opinions diverge on whether the death penalty is fairly applied.

Is the Death Penalty Applied Fairly?

This is an open question. Earlier this year in a death penalty case, Justice Breyer argued that it is “highly likely that the death penalty violates the Eighth Amendment.” Let us know what you think. Find us at feedback@plot.ly and @plotlygraphs.

Matt is speaking at Extract Conference in San Francisco, 30th October 2015. Use the discount code Extract-Plotly” to get 10% off tickets.



"The United States is the only country in the G7 (major advanced economy) to still execute people. " -What about Japan? They just executed someone this year (25 June 2015).

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