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The Problem with Bivariate Regression

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by David In the debate over guns and gun control, many types of evidence are put forward to support either side of the isles' arguments. People post studies, scatterplots, bar charts, etc. to support their arguments about why guns are good or bad for society. In this post, I'll go over the "bivariate regression, " which usually comes in the form of one posting a scatterplot plotting guns or number of gun control laws against some outcome variable.  The bivariate regression tells us little about the relationship between variable X and variable Y. Firstly, I know it doesn't need to be repeated, but correlation is not causation. This means that two variables can be positively correlated with each other (usually represented by some R^2 value), but that does not mean the independent variable causes the dependent variable to change. You can find all sorts of " spurious correlations " online that any reasonable person would correctly conclude have no causal re...
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Florida Proposes Constitutional Carry

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by David In Florida, the speaker of the House, Paul Renner, just introduced a bill that would make Florida a permitless or "Constitutional Carry" state. This means that Florida would join 25 other states in establishing this type of law. As for the empirics, I go through them in this post here on Gun Audit. Overall, I come to the conclusion that we don't have enough data to make definitive claims about the likely effects of the law. However, we do know about the effects of shall-issue or right-to-carry (RTC) laws, where one has to obtain a permit before legally concealed carrying in public.  I have a feeling that, if the bill passes, the same type of scenario is going to play out as when Florida passed its RTC law in 1987: politicians and pro-control advocates claiming the law will send crime soaring and the crime rate not ending up soaring.  Here, using the CDC WONDER database, I graph out Florida vs. neighboring states' homicide rates both pre and post-RTC law. Th...
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What Do We Know About Permitless Carry?

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by David The changes in states’ right-to-carry (RTC) laws over the last few decades has been truly phenomenal. In  1986 , many conservative states such as Florida, North Carolina, Tennessee, and Texas were “no-issue” states, meaning that a person was not legally permitted to carry a concealed weapon in public. Now, in  2023 , every state allows citizens to carry weapons in public with a permit, while 25 states do not require any permit to carry. This dramatic change in laws over the years has fueled  intense  academic and public debate over RTC laws and their effects on crime. More recently, since many states have been moving to  permitless  carry laws, a new debate has sparked: What effect do permitless carry laws have on crime rates? The first and most important thing that I will note is that there is currently no evidence that permitless carry laws increase the rate of gun carrying among criminals or non-criminals alike. Therefore, we have no real reason...
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On RAND’s Recent Report

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by David  Recently, the RAND Corporation released the Third Edition of their “Science of Gun Policy”  report . Essentially, the report sets criteria for what studies they choose to analyze, calculates their effect sizes (using  incident rate ratios  and confidence intervals). Then, based on the direction and size of the effect they judge whether the evidence for a relationship between a given law and a crime is “inconclusive,” “limited,” “moderate,” or “supportive.”    In this post, I want to focus on their evidence and conclusions they present in Chapter 18, their section on concealed carry laws. They present 12 studies on the effect of shall-issue or permitless carry vs. may- or no-issue laws. Only 3 studies find a homicide-increasing effect ( Fridel (2021) ,  French and Heagerty (2008) , and  Doucette, Crifasi, and Frattaroli (2019) ); all the other studies find no significant effect (e.g., the CI crosses 1.00). Interestingly, despite 75% of th...
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