Short iron condor strategies are expressing the view that the S&P 500 will stay in a range. They do well as long as the S&P 500 remains range bound but can do poorly during periods of extreme price moves. The Yield+ strategy uses options to trade momentum. It sells longer dated option spreads (2-3 months) to monetize the upward drift in the US equity market. It does well when the S&P 500 trends higher over longer periods of time.