Correlations

Spend much time debating gun rights on-line, and you’ll be told that “stronger” gun laws correlate to better outcomes in terms of deaths.

All right, let’s find out. I’m drawing data from the following sources:

1. Homicide rates by state, 2013: http://www.deathpenaltyinfo.org/murder-rates-nationally-and-state

Numbers are homicides per 100,000.

2. Suicide rates by state, 2012: http://www.worldlifeexpectancy.com/usa/suicide

Numbers are suicides per 100,000.

3. Brady Campaign state scorecard, 2013: http://www.bradycampaign.org/2013-state-scorecard

Their methods are their own, but since they are opposed to gun rights, I presume that their scoring favors gun control over loose gun laws.

Both graphs use an X axis with values from 0 to 4 and a Y axis from 0 to 30. The X values are keyed to a four-point grade scale:

A: 4
A-: 3.75
B+: 3.25
B: 3
B-: 2.75
C+: 2.25
C: 2
C-: 1.75
D+: 1.25
D: 1
D-: 0.75
F: 0

The Y numbers are suicides or homicides per 100,000.

First the homicide numbers compared to the Brady score:

Homicide to Brady score

Notice the lack of a pattern, other than groups of states with the same gun laws having homicide rates at wild variance from each other? If the Brady Bunch were correct, there should be a strong correlation, not nothing.

Now let’s consider the suicide numbers:

Suicide to Brady score

Here, there is a low negative correlation, though as with homicide rates, the large grouping at X = 0 is significant.

Of course, as any student of statistics knows, correlation doesn’t imply causation. But if there is causation, there must be correlation. The lack of correlation in homicide rates and the weak correlation in suicide rates demonstrates that we cannot claim that the strictness of gun laws determines lives saved.

Feel free to share this next time you’re dealing with someone promoting gun control.

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2 thoughts on “Correlations

  1. Scott Belford

    There are many more explanatory variables than the two you account for, such as state average temp, avg male population, etc (this is homicide specific, btw). While your outcome for homicides is roughly right, there is a positive correlation for rate of gun ownership and homicides, it wasn’t strong enough to hang my hat on.

    Your outcome for suicides, however, is backwards. 1st, there is a strong positive correlation between suicide rate and ownership rate, after you control for other variables and 2nd, there is a strong correlation between gun ownership rate and state gun laws; the better the gun laws, the lower the ownership rate.

    See the series beginning with http://myesoteric.hubpages.com/hub/More-Guns-More-Violent-Crime-and-More-Homicides-by-Gun-It-Is-As-Simple-As-That (as I said in the Twitter post, I had to change the title because, it turned out there is no correlation between ownership and Violent Crimes. There is a slight positive one for Homicides but that is balanced with a slight negative one for Robberies.)

    Reply
    1. Greg Camp

      You say, “the better the gun laws, the lower the ownership rate.” I disagree. Better laws allow people to exercise their rights.

      And notice how the data line up? See those clusters of varying rates of homicide or suicide despite having the same Brady score? That tells me something is agley. If gun laws work as promised, there should be a strong trend with no wild variations in clusters.

      But as you say, the data don’t support the claim made by gun control groups, so that leaves me wondering why you support gun control.

      Reply

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