The pullback since May 2015
Since its May 2015 all time high, SPX has been making lower highs and lower lows, tracing out a rounded top decline to its Feb 2016 low. The subsequent rebound has now brought SPX back to the upper edge of this rounded top (Chart 1). Interestingly, each major swing since May is likely best counted as an ABC structure (Chart 1 blue), perhaps including the current rebound (Feb-Apr, see Chart 2). If the Feb 2016 low around 1810 is to be retested or exceeded (perhaps to conclude wave -down since the 2009 bottom), another ABC type of downswing is a reasonable possibility.
Perhaps price dynamics behind the above observation is contributing to the rather slow and corrective-looking decline off the rebound high. Chart 2 highlights the initial decline potentially as a small-flat (blue), a larger flat (gray) or an LDT still in its wave B-up (not shown).
Under a (very) bullish interpretation, the current upswing is still in a small degree fourth wave (Chart 3) and should subdivide higher to complete wave C-up of an upward flat since the Aug 2015 low (Chart 1 gray) or wave (1)-up of wave -up with the Feb low being the low.