The response of illicit drug consumers to large-scale policy changes, such as legalization, is heavily mediated by their demand behavior. Since individual drug use is driven by many unobservable factors, accounting for unobserved heterogeneity is crucial for modeling demand and designing targeted public policies. This paper introduces a finite Gaussian mixture of Exact Affine Stone Index (EASI) demand systems to estimate the joint demand for marijuana, cocaine, and basuco (cocaine residual or "crack") in Colombia, accounting for corner solutions and endogenous price variation. Our results highlight the importance of unobserved heterogeneity in identifying reliable price elasticities. The method reveals two regular consumer subpopulations: "safe" (recreational) and "addict" users, with the majority falling into the first group. For the "safe" group, whose estimates are precise and nationally representative, all three drugs exhibit unitary price elasticities, with cocaine being complementary to marijuana and basuco an inferior substitute to cocaine. Given the low production cost of marijuana in Colombia, legalization is likely to drive prices down significantly. Our counterfactual analysis suggests that a 50% price decrease would result in a \$363 USD gain in utility-equivalent expenditure per representative consumer, \$120 million USD in government tax revenue, and a \$127 million USD revenue loss for drug dealers. Legalization, therefore, has the potential to reduce the incentive for drug-related criminal activity, the current largest source of violent crime in Colombia.

翻译：非法毒品消费者对大规模政策变化（如合法化）的反应，很大程度上受其需求行为的调节。由于个体吸毒行为受许多不可观测因素驱动，考虑未观测异质性对于建模需求和设计有针对性的公共政策至关重要。本文引入有限高斯混合的精确仿射斯通指数（EASI）需求系统，以估计哥伦比亚大麻、可卡因和巴苏科（可卡因残渣或“快克”）的联合需求，同时考虑了角点解和内生价格变化。我们的结果强调了未观测异质性在识别可靠价格弹性方面的重要性。该方法揭示了两个常规消费者亚群体：“安全”（娱乐性）用户和“成瘾”用户，其中大多数属于第一组。对于估计精确且具有全国代表性的“安全”组，所有三种毒品均表现出单位价格弹性，其中可卡因与大麻互补，而巴苏科是可卡因的劣质替代品。鉴于哥伦比亚大麻的生产成本较低，合法化很可能导致价格大幅下降。我们的反事实分析表明，价格下降50%将导致每位代表性消费者的效用等价支出增加363美元，政府税收增加1.2亿美元，毒贩收入损失1.27亿美元。因此，合法化有可能减少毒品相关犯罪活动的诱因，这是当前哥伦比亚暴力犯罪的最大来源。