From: coxb@netcom.com (Brian Cox) Subject: University of Maryland study (text) To: ca-firearms-owner@shell.portal.com Date: Sun, 19 Mar 1995 20:01:45 -0800 (PST) Jeff, here is the entire text of the University of maryland CCW study. OCR and editing credits are noted. As it is rather long, I thought you might want to put it up on your FTP site and just post a pointer. This is plantext only. #include ~/temp/study.txt OCR performed by dfw@netcom.com Final editing by coxb@netcom.com Original report released 13 Mar 95 Address ommisions or corrections to coxb@netcom.com ------------------------------------------------------------------------- Easing Concealed Firearm Laws: Effects on Homicide in Three States David McDowall Colin Loftin Brian Wiersema January l995 Violence Research Group Discussion Paper 15 Department of Criminology & Criminal Justice 2220 Samuel Lefrak Hall College Park, Maryland 20742-8235 301/ 405-4735 I. lNTRODUCTION Restrictions on carrying conceled weapons are among the most common types of gun control policies. These statutes limit the number of persons allowed to have deadly weapons-usually handguns-when they are outside their homes. By reducing access to guns in public, concealed weapons laws seek to make firearms less available for violence. Areas vary greatly in the details of their concealed weapon laws, but most approaches fall into two categories. One of these is a discretionary system, sometimes called "may issue" licensing. Here legal authorities grant licenses only to citizens who can establish a compelling need for them. The other approach is a non-discretionary, or "shall issue," system. Here the authorities must provide a license to any applicant who meets specified criteria. Because legal officials are often unwilling to allow concealed weapons, adopting a shall issue policy usually will increase the number of persons with permits to carry guns. In 1985 the National Rifle Association announced that it would lobby for shall issue laws. Several states. including Florida. Mississippi, and Oregon, have since changed from may issue to shall issue systems. Advocates of shall issue policies argue that they will prevent crime, and suggest that they have reduced homicides in areas that adopted them. In this article we examine the frequency of homicides in urban areas of Florida, Mississippi, and Oregon, before and after their shall issue laws began. We find no support for the idea that the laws reduced homicides instead, we find evidence of an increase in firearm murders. Part II of this article discusses concealed weapon laws in the three states. Part III considers possible effects of shall issue licensing on crime and describes the existing evidence. Part IV presents our research design, and Part V contains our findings. Part VI discusses the results and notes areas for future research. II. THE LAWS On October 1, 1987, Florida adopted a shall issue law that greatly expanded the number of persons allowed to carry concealed guns.' The new statute required the state to grant a concealed weapon license to any qualified adult who had taken a firearm safety course. Disqualifying traits included nonresidence, a history of drug or alcohol abuse, felony conviction, mental illness, and physical inability to use a gun. Previously, county officials in Florida had set their own standards for concealed carrying. Throught the state, about 17,000 persons had permits, including 1,909 in Dade county (Miami) and 25 in Hillsborough county Tampa). The rose steadily after the new law, reaching 141,000 in September 1994. Mississippi adopted a shall issue law on July 1, 1990. 11 Mississippi law was largely identical with Florida's, except that it did not require firearm safety training. Mississippi's earlier law highly restrictive, generally allowing only security guards to have concealed weapons. 12 By November 1992, the state had issued 5,136 of the new licenses. Oregon adopted a shall issue law on January 1, 1990, in a compromise between supporters and opponents at stricter gun control measures. Oregon's new law required every sheriff to provide a concealed handgun license to any qualified adult who had taken a firearm safety course. Disqualified were persons with outstanding arrest warrants or on pretrial release, persons with a history of mental illness, and persons with felony or recent misdemeanor convictions. While it eased laws on concealed carrying, Oregon tightened requirements for buying a gun. Oregon's old law barred convicted felons from owning handguns. The new law extended the ban to all firearms and to most persons ineligible for a concealed handgun license. Oregon's new law also lengthened the waiting period for handgun purchases, and required more detailed background checks. Before the law. Oregon's sheriffs issued concealed handgun licenses at their discretion. In 1993, there were fewer than 500 licensed carriers in Clackamas, Moltnomah, and Washington counties, the core of the Portland metropolitan area. 15 By October 1993, The number of licenses in these counties grew to 16,000. III. POSSIBLE EFFECTS OF SHALL ISSUE LICENSING ON CRlME The shall issue policies clearly increased the number of persons licensed to carry concealed weapons in Florida, Mississippi, and Oregon, the effects of these laws on crime are less obvious. There are grounds to believe that crime might increase, decrease, or remain the same after a shall issue law begins. Shall issue licensing might reduce crime by deterring criminal offenders. Criminals generally wish to avoid victims who may be carrying guns. 17 Knowledge that many citizens have concealed weapons thus could discourage attempts at crime, especially crimes against strangers and In public areas. On the other hand, shall issue licensing might raise levels of criminal violence. This is so because it increases the number of persons with easy access to firearms. Zimring and Cook argue that assaults are often impulsive acts involving the most readily available weapons. Guns are especially deadly weapons. and higher numbers of firearm carriers could therefore result in more homicides. Advocates of shall issuer licensing often cite figures showing that few legal carriers misuse their guns. Yet greater tolerance for legal carrying may lead to higher levels of illegal carrying as well. For example, criminals have more reason to carry firearms-and to use them-when their victims might be armed. Further, if permission to carry a concealed weapon is easy to obtain, citizens and law enforcement officials may be less apt to view illegal carrying as a serious offense. Yet shall issue licensing also may be irrelevant to crime. Even in areas with shall issue policies, only small fractions of adults have licenses to carry guns. Many citizens keep guns in their homes, and police officers often carry guns when off duty and in plain clothes. The increase in available firearms due to shall issue policies may be of little consequence. Most empirical discussions of shall issue licensing compare homicides in Florida before and after the beginning of its law. Homicide is the most accurately recorded crime, reducing the influence of measurement error on the comparison. Florida adopted its law earlier than did the other states, providing more time to study the effects. The results of the existing comparisons differ with the period that they examine. However, all comparisons find that Florida homicides decreased after the state's shall issue law began. The National Rifle Association, for example, notes that Florida's homicide rate fell by 21 percent when comparing 1987 with 1992.~~ Although the Florida experience appears to support a deterrent effect, the existing comparisons suffer from several weaknesses. First, these studies all use Uniform Crime Report data compiled by the Federal Bureau of Investigation (FBI). In 1988, the FBI did not publish crime counts for Florida. Evaluations based on the FBI data thus must ignore 1988 or use estimates of the 1988 total. This is important, because 1988 was the first full year after the law. Second, the existing evaluations use short time series of annual data. Even in Florida, there are few annual observations after the law began, and most comparisons also include only a few years before the law. Crime increases and decreases over time due to the operation of many factors. Comparisons using short time series thus are highly prone to the influence of chance events that briefly push homicides above or below their average levels. Third. the existing comparisons examine total homicide rates for the entire state. If some areas respond differently to the laws than do others. a statewide analysis may miss important effects. For example, the influence of the shall issue laws may be greatest in urban settings, where crime is most prevalent including rural areas in an analysis would then make it more difficult to detect changes in violence. similarly, combining firearm and other weapon homicides might mask effects unique to one type of murder. In short, current evaluations leave much room for doubt about the effects of the Florida law, These evaluations also neglect the outcomes of the shall issue laws in Mississippi and Oregon. A more detailed analysis using data from all three states would allow stronger inferences about the impact of the policies. IV. RESEARCH DESIGN A. STUDY DESIGN AND DATA Similar to existing evaluations of shall issue licensing, we used an interrupted time series design to study average homicide levels before and after shall issue policies began. ~~ In contrast to either work. we analyzed monthly homicide events, and we examined several urban areas within Florida, Mississippi, and Oregon. To Find if the laws differently [influenced gun deaths, we separately studied firearm homicides and homicides by-other means. We conducted analyses for Dade (Miami), Duval (Jacksonville), and Hillsborough (Tampa) counties in Florida, and for Hinds (Jackson) county In Mississippi. Because there were relatively few homicides in Multnomah county (Portland), we combined data for Clackamas, Multnomah, and Washington counties in Oregon. For each area. we used death certificate data compiled by the National Center for Health Statistics (NCHS) to count monthly homicides through December 1990. ~~ Health departments In Florida Mississippi, and Oregon provided additional cases from January 1991, to December 1992. Except in Miami, we studied the period between January 1973 and December 1992 (240 months). Miami homicides increased sharply in May 1980. following an influx of refugees from Cuba. Miami's monthly homicide totals appeared to stabilize by late 1982. and we thus analyzed the period from January 1983 through December 1992 (120 months). In total, there were 177 observations before the law in Jacksonville and Tampa. and 57 observations before the law in Miami, For all three Florida cities there were 63 observations after the law, in Mississippi there were 210 pre-law months and 30 post-law months. In Oregon there were 204 pre-law months and 36 post-law months. To remove the effects of systematic variation from each time series, we developed autoregressive integrated moving average (ARIMA) noise models. ~~ The noise models allow for variables such as poverty or age structure that influence homicides both before and after the legal changes. If not controlled, these variables may operate to bias inferences about the laws. After developing suitable noise models, we added intervention models to measure changes in homicides following the laws. a We considered three intervention models: an abrupt permanent change model, a gradual permanent change model, and an abrupt temporary change model. 27 For each series, the abrupt permanent change model Provided the best fit, to the data. Our analysis avoids the major problems of previous comparisons. The NCHS data collection system is independent of the FBI. allowing us to use 1988 Florida homicide counts. The long monthly time series provide more stable estimates of homicide patterns before and after the shall issue laws began. By studying firearm and other weapon murders separately in several areas, we can more precisely isolate any effects. B. THREATS TO VALIDITY AND SUPPLEMENTARY ANALYSES lnterrupted time series studies are among the strongest non- experimental research designs. 30 Still, as is true with any design, time series studies do not eliminate all threats to valid inference. Perhaps the most important threat to the design's validity is what Cook and Campbell call history. This refers to the possibility that a permanent change In another variable produced an observed effect. For example, suppose that each area adopted other, policies that influenced crime when they began their shall issue laws. These policies would then be confounded with the laws, and they would be historical threats to validity. The major method that we use to avoid historical threats is to replicate the analysis in five areas. An unnoticed historical event may have increased or decreased homicides in any single area after its shall issue law began. Yet if similar outcomes occur in several areas after the laws, historical events become less plausible explanation of the change. In the face of a consistent pattern of results, historical explanation would require permanent changes in other variables in each area at about the time its law began. Further, these changes would have to operate in the same way in each area, always increasing or decreasing homicides. The areas in our study are geographically separated and demographically diverse, and they adopted their laws at three different times. While the replications cannot entirely rule out history, a constant set of results would greatly narrow the range of events that could account for an effect. On the other hand, a varied pattern of results, with large increases or decreases in only one or two areas, would be consistent with history. Beyond replication, we used two additional methods to evaluate historical threats, First, we searched for other legal changes, especially changes in firearm laws, which might affect homicides. The most important laws that we identified regulated handgun sales in Florida. The states adopted background checks of potential handgun buyers in' February 1991, and it began a waiting period for purchases in October 1991. ~~ Florida's waiting period and background check laws began more than three years after shall issue licensing. and one might expect them to have little influence on the results. Still, we included these laws in a supplementary analysis to verify that their effects had similarly influenced rates across all areas in a given year. ~~ We then included intervention variables to measure the effects of the shall issue and (for the Florida cities) background check and waiting period laws. V. RESULTS Estimates of the effects of the shall issue laws on the monthly homicide counts appear in table 1. To simplify the presentation, we report only the means before the laws and the changes in homicides after the laws began. ~~ The results in table 1 show that firearm homicides increased in four of the five areas in the post-law period. Except the lancers in Miami and the decrease in Portland, these changes were statistically significant (p < .05). Expressed as percentages, the changes varied from a decrease of 12 percent (Portland) to an increase of 74 percent (Jacksonville).` ' Considering each area as a replication of the same experiment, gun homicides increased by an average of 26 percent. An inverse normal combined test of statistical significance easily rejected the null hypothesis of zero overall change. In contrast to homicides, homicides by other means did not show a consistent pattern or variation. Homicides without firearms increased in Tampa and Jacksonvllle, but they fell In the other three areas. Across all five areas, the average change In homicides without guns was [LESS ?] than 1 percent. In combination, this change was statistically insignificant. Table 2 contains the analysis for the Florida cities that includes the state's waiting period and background check laws. These results provide no evidence that the original estimates were due to confounding between the other laws and shall issue licensing, Adding the other laws lightly increased the coefficients for the shall issue policy, but it did not alter inferences about the effect in any city. Although not central to our study, It is worth note that the levels of each Florida firearm series decreased after the waiting period and background checks began. Yet homicides without guns also fell in two cities, and the policies should influence only firearm crimes. the results thus do not point to any strong conclusions about the waiting period and background check laws. Table 3 presents the analysis that adds national homicide counts as a cavort. in each area, there was a positive relationship between local homicide patterns and patterns in the nation. Still, including the national counts only modestly changed the estimates for shall issue licensing. Finally, Table 4 reports the results for the annual homicide rates. Here the coefficient for the shall issue policies is the average effect across all five cities. Gun homicides increased on average by 4.5 per 100,000 persons, a value significantly different from zero. In contrast, murders without guns decreased insignificantly. Gun homicides fell insignificantly following Florida's waiting period and background check laws, while other weapon homicides increased. VI. DISCUSSION Across the five areas, firearm homicides increased in the aftermath of the shall issue laws. In, contrast, homicides without guns remained steady, these findings were little altered when we considered other laws. controlled for variations in national homicide counts, and allowed for population changes. The pattern of results leads us to two conclusions, one stronger than the other. The stronger conclusion is that shall issue laws do not reduce homicides, at least in large numbers. If there were such a decrease, other events would have to push murders up strongly enough to mask it in all five areas that we studied. Such events are possible, of course, but we believe that they are extremely unlikely. The weaker conclusion is that shall issue laws raise levels of firearm murders. Coupled with a lack of influence on murders by other means, the laws thus increase the frequency of homicide. u This interpretation agrees with other work showing that policies to discourage firearms in public may help prevent violence. For example, studies by Pierce and Bowers. and by O'Carroll et al. found that laws providing mandatory sentences for illegal gun carrying reduced firearm crimes in Boston and Detroit. Similarly, Sherman et al. found that gun crimes fell during a Kansas City program that confiscated firearms from people who carried them outside their homes. Despite this evidence, we do not firmly conclude that shall issue licensing leads to more firearm homicides. This is so because the effects varied over the study areas. Firearm homicides significantly increased in only three areas, and one area witnessed an insignificant decrease. In combination, the increase in gun homicides was large and statistically significant. Yet we have only five replications, and two of these do not clearly fit the pattern. The statistical significance of the combined results aside, the analysis implies that shall issue policies do not always raise levels of gun murder. sometimes, at least, local conditions operate to blunt any effects. The areas without significant increases (Portland and Miami) may be unusual, but we lack the data to examine whether this is true. Stated in another way, we cannot completely dismiss historical events as an explanation of the increase in firearm murders. One would need a complex theory to explain how history could mask a decrease in homicides after the laws. Historical accounts of the apparent increase might be much simpler. A more definitive analysis should be possible in the future. Besides Mississippi and Oregon, six other states have adopted shall issue laws based on the Florida model. four of these states - Alaska, Idaho, Montana and Wyoming - have small populations and low levels of criminal violence. 44 As a result, It would be difficult to perform a statistically meaningful analysis of changes in homicides after their laws began. Yet two more populous states, Arizona and Tennessee, enacted shall issue licensing in 1994. Given several years of experience with the laws in these states, future research could provide more certain estimates of the effects on firearm violence. The legislatures of other states. including Colorado, Louisiana, and Texas, also have seriously considered shall issue statutes. 45 Given this level of interest, it is likely that shall issue licensing will continue to receive attention. While our analysis does not allow a firm conclusion that shall issue licensing increases firearm homicides, it does suggest caution about these laws. Some observers consider strict limits on firearms outside the home to be among the most effective forms of gun control. 47 beyond any influence on violence, the policies are easy to enforce and they do not inconvenience most gun owners. When areas weaken limits on concealed weapons, they thus may be giving up a simple and effective method of preventing firearm deaths. Table 1. Mean Numbers of Homicides per Month, By Jurisdiction and Method, Before and After Implementation of Shall Issue Licensing Type of Before the Homicide Shall Issue Change After the Shall Issue Law and Location Law no./mo. no./mo. SE % l-Stat Firearm Miami 25.88 0.79 1.89 +3 0.73 Jacksonville 6.24 4.61 0.5 +74 7.81 Tampa 4.91 1.10 0.44 +22 2.50 Portland area 2.79 -0.34 0.35 -12 -0.98 Jackson 3.64 1.57 0.47 +43 3.34 Mean change = +26.0% lnverse normal combined Z = -5.99. p < .0001 Other Methods Miami 9.58 -0.73 0.63 -8 -1.16 Jacksonville 2.85 1.03 0.32 +36 3.22 Tampa 2.74 0.48 0.42 +17 1.14 Portland area 2.46 -0.58 0.38 -24 -1.53 Jackson 1.34 -0.30 0.27 -22 -1.11 Mean change = -0.2% lnverse normal combined Z = +0.25, p = .0023 Difference between the mean number of homicides per month before implementation of the shall Issue law and the mean number after its implementation. Table 2. Mean Numbers of Homicides per Month In Florida Areas, By Jurisdiction and Method, Before and After Implementation of Shall Issue Licensing and Waiting Period and Background Check Laws Type of Before Change After the Change After the Homicide and the Shall Issue Law Waiting Period and Location Laws Background Check Laws no/mo no/mo SE l-Stat no/mo SE l-Stat Firearm Miami 25.88 2.25 1.19 1.89 -3.99 1.51 -2.64 Jacksonville 6.22 6.10 0.61 10.00 -3.25 0.90 -3.61 Tampa 4.91 1.35 0.52 2.60 -0.68 0.77 -0.88 Other Methods Miami 9.60 0.11 0.53 0.21 -2.48 0.68 -3.65 Jacksonville 2.86 1.25 0.38 3.29 -0.60 0.56 -1.07 Tampa 2.72 0.52 0.44 1.18 0.07 0.65 0.11 Difference between the mean number of homicides per month before Implementation of the shall issue law and the mean number after its implementation, controlling for the waiting period and background check laws. Difference between the mean number of homicides per month before Implementation of the waiting period and background check laws and the mean number after their implementation, controlling for the shall issue law. Table 3. Mean Numbers of Homicides per Month, By Jurisdiction and Method, Before and After Shall Issue Licensing, Controlling for Mational Homicide Counts. Type of Constant Change After the Coefficient for National Homicide and Shall Issue Law Homicide Counts Location no./mo no./mo SE l-Stat Slope SE l-Stat Firearm Maimi 25.86 1.55 1.12 1.38 0.0144 0.0063 2.29 Jacksonville 6.23 5.43 0.62 8.76 0.0017 0.0020 0.85 Tampa 4.91 1.17 0.49 2.39 0.0014 0.0015 0.93 Portland area 2.80 -0.44 0.42 -1.05 0.0015 0.0014 1.07 Jackson 3.62 1.61 0.57 2.82 0.0011 0.0013 0.85 Other Methods Miami 9.62 -0.43 0.55 -0.78 -0.0010 0.0051 0.20 Jacksonville 2.86 0.96 0.35 2.74 0.0181 0.0214 0.85 Tampa 2.72 0.88 0.41 2.15 0.0072 0.0202 0.37 Portland area 2.62 -0.28 0.43 -0.65 0.0039 0.0019 2.05 Jackson 1.35 0.22 0.27 0.81 0.0027 0.0013 2.08 Difference between the mean number of homicides per month before implementation of the shall issue law and the mean number after its implementation, controlling for national homicide counts. Slope estimate for influence of national homicide counts, controlling for the shall issue law. Table 4. Pooled Annual Homicide Rates, Before and After Implementation of Shall lssue Licensing and Waiting Period and Background Check Laws. Firearm Homicide Rate Per 100,000 Coefficient SE t-Stat Estimate Shall Issue Licensing 4.52 2.58 1.75 Waltinq Period and -3.25 2.09 -1.55 Background Check Constant 11.20 0.53 21.13 Other Methods Homicide Rate Per 100,000 Coefficient SE t-Stat Estimate Shall Issue Licensing -0.16 0.75 -0.21 Waiting Period and 1.81 2.01 0.90 Background Check Constant 5.02 0.23 21.83 [end]