The preferred count, one of several credible tracking counts, places SPX in a fourth wave pullback with respect to the key Feb 2016 low. See chart.
There are two key potential structures of the current fourth wave pullback.
 While an expanded flat to MA200 (green 4) makes more sense in terms of the local structure, it fails to alternate with wave 2. That leaves us with two key possibilities within this scenario - (a) [iii] but not 3 topped in early March (b) wave 4 is a complex combo (expanded flat-x-something).
 A shallow triangle (blue S4). Since this past week's one-day sell-off is most likely an impulse wave, we likely saw wave (a)-down and (b)-up of wave [c]-down on Thursday and Friday.