ver the past 10 years, the U.S. energy sector has exerted substantial influence on overall U.S. business fixed investment. From 2010 to 2014, a time when energy production in the United States was expanding, investment in the energy sector was a boon to aggregate investment. However, following the sharp oil price decline in 2014, the energy sector was a drag on aggregate investment. These recent examples demonstrate that the energy sector can contribute both positively and negatively to overall investment activity in the United States. Assessing the energy sector's contribution to investment requires an understanding of the size of the energy sector relative to the overall economy, the contributions from individual segments of the energy sector, and how investment dynamics within these segments have changed over time. Energy sector technology advanced rapidly over the last decade, a period when U.S. energy activity and investment also expanded. These technological changes contributed to increased investment variability within some energy segments. Together, changing energy activity and shifting variability within segments of the energy sector can meaningfully alter both the level and variability of aggregate investment. In this article, I estimate how individual segments of the energy sector contribute to U.S. aggregate investment activity as well as how those contributions have shifted over time. I find that levels of investment Energy Investment Variability within the Macroeconomy