Source

Modification

Violent Crime

Murder

Rape

 

Standard errors

Lott (2000)

Unadjusted standard errors

0.98

1.57

1.22

Duggan

State clustered standard errors

2.31

2.95

2.32

Helland and Tabarrok

Placebo standard errors

4.9

6.4

5.6

aUses clustered sampling standard errors.

bAdded covariates for state poverty, unemployment, death penalty execution rates, and regional time trends.

TABLE 6-4 Summary of Selected Studies: Trend and Hybrid Variable Model (shaded cells indicate a positive coefficient)

Source

Modification

Violent Crime

Murder

Rape

Lott (2000)

Original specification and data

2*

–3*

–1*

Lott (2000)a

1977-1996

–2*

–2*

–3*

Ayres and Donohue (2003a)

Hybrid model: Level

Trend

7*

–2*

3

–5*

7*

–3*

 

1977-1997 data: Level

Trend

0

–2*

7*

–4*

6*

–3*

Plassmann and Whitleya,b

Regional trend + others 1977-2000 data

–1

–2

–3*

Ayres and Donohue (2003b)a,b

Regional trends + other controls 1977-2000 corrected data

0

–2

–2

aAdded covariates for state poverty, unemployment, death penalty execution rates, and regional time trends.

bStandard errors adjusted for state clustering.

its murder rate. The estimated changes in the murder rates of other states that adopted right-to-carry laws are sometimes positive (three cases) and sometimes negative (five cases) and are not statistically significantly different from zero. Black and Nagin also report variations in the directions and statistical significance of changes in the rates of rape and aggravated assault. They report no statistically significant increases in robberies, but only 2 of the 10 states that adopted right-to-carry laws had statistically signifi-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement