|
Article Excerpt
Abstract
This paper identifies the determinants affecting the adolescent populations' decision regarding whether or not to consume illegal drugs. The authors estimate a simultaneous Type II Tobit model for each sample substance, including marijuana, LSD, amphetamines, cocaine, volatile substances, and heroine. The data are drawn from three Spanish Surveys on Drug Use in the School Population conducted in 1994, 1996, and 1998. The results indicate that illegal drug use among Spanish adolescents is clearly determined by economic variables. It is similarly determined by other sociodemographic variables, such as personal habits, family environment, and the receipt of information regarding the negative consequences of drug use. (JEL D81, I10, K42, D12)
Introduction
The use of illegal drugs, particularly among adolescents, imposes a number of individual and social costs. These include increased crime [Silverman and Spruill, 1977; Simonds and Kashani, 1980; Benson et al., 1992; Resignato, 2000], health problems [Tommasello, 1982; Nahas and Latour, 1992; Polen et al., 1993; Pope et al., 1995], and employment or school difficulties [White et al., 1988; Kaplan and Liu, 1994; Yamada et al., 1996; Mijares, 1997; Mensch and Kandel, 1988; Bray et al., 2000; MacDonald and Pudney, 2000a, b; 2001; French et al., 2001]. Apart from these clearly significant aspects, two additional factors require analysis: (1) the addictive nature of drug use, where individuals who have started to consume find that they cannot quit the habit and must go on consuming [DeFonseca et al., 1997; Grossman and Chaloupka, 1998; Samhsa, 1998] and (2) the testing of the gateway theory, which states that there is a systematic sequencing in the use of addictive substances that begins with alcohol and cigarettes, continues on to marijuana, and leads finally to hard drugs such as cocaine, heroine and LSD [Chaloupka and Laixuthai, 1997; DeSimone, 1998].
In addition to these studies, which reflect the socioeconomic relevance of illegal drug abuse, papers published by [Gill and Michaels, 1991] and [Saffer and Chaloupka, 1999] provide specific and significant evidence on the determinants of this pattern of behaviour. Gill and Michaels use the National Longitudinal Surveys of Youth corresponding to 1980 and 1984 in order to estimate a Probit equation that explains the individual decision to use illegal drugs. They find that non-economic factors dominate the decision to participate in the illegal drug market. Saffer and Chaloupka employ the National Household Surveys of Drug Abuse corresponding to 1988, 1990, and 1991 in order to estimate various Probit specifications for different illegal drugs. Their main contribution is the use of prices to estimate price elasticities of participation, i.e., -0.28 for cocaine and -0.94 for heroin. Although these two papers undoubtedly offer relevant contributions, they both focus on the significant participation equation, assuming it is an empirical measure of consumption. However, neither one has paid any attention to the specific factors that determine the quantity of illegal drugs that the individual will demand.
The public problem of illegal drug use is a widespread phenomenon in many countries of the developed world and is especially worrying among the adolescent population. Although it is well established that illegal drug use among this age group is significant in the United States, it is also prevalent in other countries, such as Spain. A comparison of the Spanish rates derived from the Spanish Surveys on Drug Use in the School Population conducted in 1994, 1996, and 1998 with those corresponding to the U.S. homogenous participation rates obtained from the Youth Risk Behavior Surveys conducted in 1995, 1997, and 1999 confirms this reality. Indeed, the situation in Spain would appear to be even bleaker. U.S. data now reveal a decreasing trend in the adolescent use of marijuana (rates have fallen from 26% in 1995 to 24% in 1999) and a stable trend in the use of cocaine of about 3.5%. In Spain, however, participation rates in the majority of illegal drugs reflect significantly increasing trends, with marijuana and cocaine use rising from 12.8% and 1.1%, respectively, in 1994, to 17.2% and 2.4% in 1998.
A preliminary descriptive analysis of the illegal use of drugs by Spanish adolescents indicates that marijuana was the most widely used illegal drug during the 1990s (15.2%). This was followed by LSD and amphetamines (around 2.4%-2.5%), cocaine and volatile substances (around 1.5%), and heroine (0.3%). In fact, illegal drug use worsened throughout the 1990s as participation and frequency of consumption increased while the starting age decreased. It is, therefore, crucial to gain a better understanding of the socioeconomic determinants of illegal drug use among the adolescent population in Spain.
In light of the above, this paper offers evidence on the illegal drug participation and consumption decisions of Spain's adolescent population. Specifically, the authors follow Maddala [1983] by estimating a simultaneous Type II Tobit model for each of the illegal substances included in the sample, including marijuana, LSD, amphetamines, cocaine, volatile substances, and heroine. This specification includes two equations. The first models an individual's decision regarding whether or not to consume an illegal drug, while the second determines the quantity demanded if the individual decides to do so. The data source derives from three Spanish Surveys on Drug Use in the School Population conducted in 1994, 1996, and 1998.
The analysis considers a number of habitual socioeconomic factors, such as gender, age, working parents, and individual income, as well as additional relevant variables, such as whether family members smoke cigarettes, risky or healthy social behaviors, and self-evaluation about the dangers and addictive character of drugs. Such empirical results provide a better understanding of the determinants of illegal drug use among young people in Spain and must be the starting point for legislators shaping policies aimed at effective prevention.
The Data
As mentioned earlier, the data used in this work comes from three surveys conducted by the Spanish SDUSP in 1994, 1996, and 1998. The surveys offer 22,578, 19,191, and 18,346 observations, respectively, and were carried out by the Spanish Government's Delegation for the National Plan on Drugs. They contain complete information on both individual and family socioeconomic characteristics. At the same time, they offer data on a number of other factors related, for example, to school performance, harmful and healthy habits, and the effects of information on the consequences of illegal drug consumption. All of this data were obtained directly from the surveyed adolescents, who answered a complete questionnaire on...
|
