HIV Breakthroughs and Risky Sexual Behavior*
研究发现美国艾滋病治疗突破降低了死亡率，但通过改善患者健康增加了其性伴侣数量，导致感染风险上升至少44%，可能降低未感染者的预期福利。
Recent HIV treatment breakthroughs have lowered HIV mortality in the United States, but have also coincided with increased HIV incidence. We argue that these trends are causally linked, because new treatments have improved health and survival for the HIV +, increased their sexual activity, and thus facilitated HIV's spread. Using variation in state-level Medicaid eligibility rules as an instrument for HIV treatment, we find that treating HIV + individuals more than doubles their number of sex partners. A change of this magnitude would increase infection risk by at least 44 percent for the HIV-negative and likely have lowered their expected welfare.