Firearms and Murder what does the Data Tell Us?

In the wake of the horrific shooting that occurred in Sandy Hook CT, the argument over gun control has heated up again.  As always the arguments are high on emotion and short on data.  The data when presented is used to promote one side or another and can often be contradictory.  Those on the side of limiting guns say that states with stricter gun laws have fewer gun related homicides and those on the side of keeping them say that if guns were not present people would use other weapons to kill people.

According to the data both sides are right, and both sides are wrong, the story is interesting but much more complicated than either side would like to present. When you look at murders, what is the most used weapon? Based on the data from (source for firearm data: www.fbi.gov), the answer is simple, firearms.

However the answer becomes less simple if you take a closer look at the data.  If you look at state by state data there is not such a clean cut relationship between firearms and Murder.

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State	Total Murders	% Firearms	Other weapons
Hawaii	7	14.29	85.71
Vermont	8	50.00	50.00
North Dakota	12	50.00	50.00
Rhode Island	14	35.71	64.29
South Dakota	15	33.33	66.67
New Hampshire	16	37.50	62.50
Montana	18	38.89	61.11
Maine	25	48.00	52.00
Alaska	29	55.17	44.83
Idaho	32	53.13	46.88
Delaware	41	68.29	31.71
Iowa	44	43.18	56.82
Utah	51	50.98	49.02
Nebraska	65	64.62	35.38
Minnesota	70	61.43	38.57
West Virginia	74	58.11	41.89
Oregon	77	51.95	48.05
District of Columbia	108	71.30	28.70
Kansas	110	66.36	33.64
New Mexico	121	49.59	50.41
Connecticut	128	73.44	26.56
Nevada	129	58.14	41.86
Wisconsin	135	59.26	40.74
Colorado	147	49.66	50.34
Kentucky	150	66.67	33.33
Arkansas	153	71.90	28.10
Washington	161	49.07	50.93
Massachusetts	183	66.67	33.33
Mississippi	187	73.80	26.20
Oklahoma	204	64.22	35.78
Indiana	284	64.44	35.56
Virginia	303	68.65	31.35
South Carolina	319	69.91	30.09
Arizona	339	65.49	34.51
Missouri	364	75.82	24.18
Tennessee	373	65.42	34.58
New Jersey	379	70.98	29.02
Maryland	398	68.34	31.66
Illinois3	452	83.41	16.59
Louisiana	485	82.89	17.11
Ohio	488	70.49	29.51
North Carolina	489	68.51	31.49
Georgia	522	70.88	29.12
Michigan	613	73.41	26.59
Pennsylvania	636	73.90	26.10
New York	774	57.49	42.51
Texas	1089	64.19	35.81
California	1790	68.16	31.84

 In some states the percentage of firearms involved in murder is high, in others it is not, however if you sort the data by number of murders, you can see that when the numbers of murders in a state is high, then most of the murders involve firearms, this is especially true when the number of murders is above 200.  When the numbers of murders are below 100, then the relationship between murders and guns is much lower.

I also looked at the relationship between gun laws (using data from The Brady Campaign), to see if there was a correlation between gun laws, number of murders and the use of firearms and murder.

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State	points	Total Murders	% Firearms
Hawaii	50	7	14.29
Vermont	6	8	50.00
North Dakota	2	12	50.00
Rhode Island	44	14	35.71
South Dakota	4	15	33.33
New Hampshire	6	16	37.50
Montana	2	18	38.89
Maine	7	25	48.00
Alaska	0	29	55.17
Idaho	2	32	53.13
Delaware	13	41	68.29
Iowa	7	44	43.18
Utah	0	51	50.98
Nebraska	5	65	64.62
Minnesota	14	70	61.43
West Virginia	4	74	58.11
Oregon	15	77	51.95
District of Columbia		108	71.30
Kansas	4	110	66.36
New Mexico	4	121	49.59
Connecticut	58	128	73.44
Nevada	5	129	58.14
Wisconsin	3	135	59.26
Colorado	15	147	49.66
Kentucky	2	150	66.67
Arkansas	4	153	71.90
Washington	15	161	49.07
Massachusetts	65	183	66.67
Mississippi	4	187	73.80
Oklahoma	2	204	64.22
Indiana	4	284	64.44
Virginia	12	303	68.65
South Carolina	8	319	69.91
Arizona	0	339	65.49
Missouri	4	364	75.82
Tennessee	8	373	65.42
New Jersey	72	379	70.98
Maryland	45	398	68.34
Illinois3	35	452	83.41
Louisiana	2	485	82.89
Ohio	7	488	70.49
North Carolina	16	489	68.51
Georgia	8	522	70.88
Michigan	25	613	73.41
Pennsylvania	26	636	73.90
New York	62	774	57.49
Texas	4	1089	64.19
California	81	1790	68.16

The numbers in the points column are points given to each state according to how comprehensive their gun laws are, the higher the number the stronger the gun restrictions.  Considering that the two states that have one of the best and worst records on gun control have the highest number of murders and both have high levels of involvement of firearms in murders, and many states with very lax gun laws also have some of the lowest murder rates, it is hard to see any kind of correlation between gun laws and murder rates, or rates of firearms used in murders base on this data.

  A word of caution for those gun enthusiasts that would like to run with this data, crime rates are often highly correlated with population rates, so a better way to tackle this question would be to look at each state individually and see data on guns and violence before and after gun laws are adopted.  Also correlation does not equal causation, so looking at New Jersey for example, New Jersey has one of the best scores on gun control, relatively high murder rates, and a high proportion of those murders involved guns.  The question is, is this despite the good gun laws? Or does this data simply reflect that those gun laws were put in place to tackle a serious problem with gun violence?

The one thing that does seem clear however, is that the more murders there are in a state, the higher the likelyhood that a gun is involved.  The three charts below show this for all the states and then for each state individually, broken down into states with less than 100 murders, states with between 100 and 200 murders and then states with greater than 200 murders.  In the graphs broken down by state the blue columns represent total murders, the red ones, the murders where firearms were involved, and the green one where something other than a firearm was involved.

The numbers were not what I expected, but I thought they were interesting.  In the following blog, we have a look at the crime rates of the US compared to other industrialized countries (America is a violent country).  Again for me what this data tells us it is not that clear cut, America is a much larger country than many other industrialized countries, does not have as substantial social safety nets, health care and ways of dealing with poverty as many other industrialized countries.  So in my mind relative crime rates need to be treated with caution.  But the data is interesting.