The Vanguard Energy Index Fund (VDE) has also added $100 million over that time frame. The Energy Select Sector SPDR (XLE) had just found its footing in the second half of 2017 as surging commodity prices boosted demand for oil and gas stocks. Investors chasing the energy theme are likely to be buoyed by the expectation of rising commodity prices, growing inflationary pressures, and the perceived value of beaten-down stocks.