One of the most notable features of any survey of the history of energy regimes in the Americas over the past century is the “pendulum effect.” Anecdotal though the observation may be, it is clear that despite the broad and incremental transformational changes that have occurred in the global energy landscape over time, individual countries have undergone wild swings in the way they have met these changes. Like the workings of a grandfather clock in the front hall of some stately home, there is a seem-ing inevitability to these alternations between market orientation and a more interventionist approach, and while time advances hour by hour in a forward motion, this momentum is always underpinned by the movement of the pendulum.In her chapter in this volume on the Mexican oil industry, Linda B. Hall quotes one opponent of the country’s 2014 energy reform, who asked in La Jornada, “When will we see the pendulum effect? How can we go back?” This individual might have been surprised to learn that in four years’ time one of the principal opponents of the project, Andrés Manuel López Obrador, would be elected president.