Source: Shutterstock Vanguard Energy ETF (VDE) Financial stocks weren't the only stocks to buy when the yield curve is flattening. For investors who can time the trade right, though, there may be a tidy little chunk of change to be pocketed from a fund like the Vanguard Energy ETF (NYSEARCA: VDE ), or maybe a specific energy stock. Upfina qualifies its finding, explaining that these stocks tend to do well in that scenario "because inflation usually increases at the end of the cycle, meaning oil prices are going up along with the other commodities."