More Guns Less Crime by John Jr (ebook reader macos .txt) 📗

reductions from being able to defend themselves. Unfortunately, however unintentionally, California's new laws risk disarming precisely these poor minorities.

Using Other Crime Rates to Explain the Changes in the Crime Rates Being Studied

Other questions still exist regarding the specifications employed here. Admittedly, although arrest rates and average differences in individual counties are controlled for, more can be done to account for the changing environments that determine the level of crime. One method is to use changes in other crime rates to help us understand why the crime rates that we are studying are changing over time. Table 4.5 reruns the specifications used to generate figure 4.1 A but includes either the burglary or robbery rates as proxies for other changes in the criminal justice system. Robbery and burglary are the violent- and property-crime categories that are the least related to changes in concealed-handgun laws, but they still tend to move up and down together with all the other types of crimes. 33

Some evidence that burglary or robbery rates will measure other changes in the criminal justice system or other omitted factors that explain changing crime rates can be seen in their correlations with other crime categories. Indeed, the robbery and burglary rates are very highly correlated with the other crime rates. 34 The two sets of specifications reported in table 4.5 closely bound the earlier estimates, and the estimates continue to imply that the introduction of concealed-handgun laws coincided with similarly large drops in violent crimes and increases in property crimes. These results differ from the preceding results in that the nondiscretionary laws are not significant related to robberies. The estimates on the other control variables also remain essentially unchanged. 35

Crime: Changes in Levels Versus Changes in Trends

The preceding results in this chapter examined whether the average crime rate fell after the nondiscretionary laws went into effect. If changes in the law affect behavior with a lag, changes in the trend are probably more relevant; therefore, a more important question is, How has the crime trend changed with the change in laws? Examining whether there is a change in levels or a change in whether the crime rate is rising or falling could yield very different results. For example, if the crime rate

Table 4.5 Using crime rates that are relatively unrelated to changes in nondiscretionary laws as a method of controlling for other changes in the legal environment: controlling for robbery and burglary rates

Table 4.5 Continued

Percent change in various crime rates for changes in explanatory variables

Violent Aggravated

crime Murder Rape assault

Change in the explanatory variable

Robbery

Property crime

Burglary Larceny

Auto theft

Controlling for burglary rates

Nondiscretionary law adopted multiplied by *county population (evaluated at mean county population)

Arrest rate for the crime category increased by 100 percentage points

-2.4%* 1%

-0.026* 5%

-4.3%* 1.1%

-0.13* 6%

-2.0%* 0.4%

-0.05*

3%

-2.6%* 0.4%

-0.05* 5%

0.4% 0.04%

-0.043* 3%

1.8%* 0.7%

-0.05* 6%

1.4%* 0.4%

-0.01* 2%

3.6%* 0.5%

-0.01* 2%

Note: While not all the coefficient estimates are reported, all the control variables are the same as those used in table 4.1, including year and county dummies. All regressions use weighted least squares, where the weighting is each county's population. Net violent and property-crime rates are respectively net of robbery and burglary rates to avoid producing any artificial collinearity. Likewise, the arrest rates for those values omit the portion of the corresponding arrest rates due to arrests for robbery and burglary. While not reported, the coefficients for the robbery and burglary rates were extremely statistically significant and positive. Entire sample used over the 1977 to 1992 period. *The result is statistically significant at the 1 percent level for a two-tailed t-test.

CONCEALED-HANDGUNLAWS ANDCRIME RATES/73

was rising right up until the law was adopted but falling thereafter, some values that appeared while crime rate was rising could equal some that appeared as it was falling. In other words, deceptively similar levels can represent dramatically different trends over time.

I used several methods to examine changes in the trends exhibited over time in crime rates. First, I reestimated the regressions in table 4.1, using year-to-year changes on all explanatory variables (see table 4.6). These regressions were run using both a variable that equals 1 when a nondiscretionary law is in effect as well as the change in that variable (called "differencing" the variable) to see if the initial passage of the law had an impact. The results consistently indicate that the law lowered the rates of violent crime, rape, and aggravated assault. Nondiscretionary laws discourage murder in both specifications, but the effect is only statistically significant when the nondiscretionary variable is also differenced. The property-crime results are in line with those of earlier tables, showing that nondiscretionary laws produce increases in property crime. Violent crimes decreased by an average of about 2 percent annually, whereas property crimes increased by an average of about 5 percent.

As one might expect, the nondiscretionary laws affected crime immediately, with an additional change spread out over time^Why would the entire effect not be immediate? An obvious explanation is that not everyone who would eventually obtain a permit to carry a concealed handgun did so right away. For instance, as shown by the data in table 4.7, the number of permits granted in Florida, Oregon, and Pennsylvania was still increasing substantially long after the nondiscretionary law was put into effect. Florida's law was passed in 1987, Oregon's in 1990, and Pennsylvania's in 1989.

Reestimating the regression results from table 4.1 to account for different time trends in the crime rates before and after the passage of the law provides consistent strong evidence that the deterrent impact of concealed handguns increases with time. For most violent crimes, the time trend prior to the passage