Objectives. To examine the relationship between Medicaid expansion under the 2010 Patient Protection and Affordable Care Act and both HIV testing and risk behavior among nonelderly adults in the United States. Methods. We pooled 2010 to 2017 data from the Behavioral Risk Factor Surveillance System and focused our main analysis on respondents aged between 25 and 64 years from families with incomes below 138% of the federal poverty level. We used the difference-in-difference method and sample-weighted multivariable models to control for individual, state-area–level, and trend factors. Results. Medicaid expansion was associated with a significant 3.22-percentage-point increase in HIV test rates (P < .01) for individuals below 138% of the federal poverty level, with the largest impacts on non-Hispanic Blacks, age groups 35 to 44 years and 55 to 64 years, and rural areas. Expansion was not related to changes in HIV-related risk behavior. Conclusions. Medicaid expansion promoted HIV testing without increasing HIV risk behavior, but there were large disparities across race/ethnicity, age, and geographic area types. Public Health Implications. Nonexpansion states, mostly in the South, might have missed an opportunity to increase HIV test rates, which could have serious future health and financial consequences.

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Amaranth Advisors LLC (Amaranth) suffered losses of $6.4 billion and failed in September 2006 as a result of its enormous spread trade bets in the natural gas futures markets and uncharacteristically large spread price movements. This financial fiasco led to a Congressional investigation, and, shortly thereafter, Amaranth was charged by the Commodity Futures Trading Commission (CFTC) and Federal Energy Regulatory Commission (FERC) with price manipulation. CFTC charged Amaranth with attempted, intraday, price manipulation in the natural gas futures market, and FERC charged Amaranth with perfected, intraday, price manipulation in the natural gas spot market. Marthinsen and Gai expanded the scope of these price manipulation charges by investigating whether Amaranth engaged in interday price manipulation during 2006. They found no convincing evidence of one-way Granger causality from changes in Amaranth's absolute positions to changes in the prices of natural gas derivatives contracts. This article expands on the interday price manipulation analysis of Marthinsen and Gai by testing for Granger causality between (1) changes in Amaranth's extreme positions and the returns on natural gas futures contracts, (2) changes in Amaranth's (calendar) spread positions and (calendar) spread prices on natural gas futures contracts, (3) changes in Amaranth's relative spread positions and spread prices, and (4) changes in Amaranth's positions and price volatility in the natural gas derivatives markets. Our results show no strong statistical evidence that changes in Amaranth's absolute, relative or extreme &

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Price manipulation in US energy markets has become a heated political and economic issue because of events such as the Enron scandal, California's electricity crisis, and volatile movements in natural gas and petroleum prices. This article tests to determine whether Amaranth Advisors LLC manipulated natural gas prices during 2006. Amaranth is of particular interest because, during 2006, it controlled as much as 80 per cent of the natural gas open interest on the New York Mercantile Exchange and InterContinental Exchange. As a result of its dominant market position and suspicious trading activities, the Commodity Futures Trading Commission (CFTC) charged Amaranth in 2007 with attempted intraday price manipulation in the natural gas derivatives market, and the Federal Energy Regulatory Commission (FERC) followed the day after with charges that the fund engaged in perfected intraday price manipulation in the natural gas spot market. This study complements the CFTC and FERC investigations by testing whether Amaranth engaged in interday price manipulation in the natural gas derivatives markets during 2006. Using Granger causality tests, we find no convincing evidence of one-way causality from changes in Amaranth's positions to changes in the prices of natural gas derivatives contracts.