On Balance Volume/Price

First, look at the chart, then read.

Use OBV/Price to see a price adjusted by 'On Balance Volume' - (OBV), a momentum indicator that measures positive and negative volume flow, was developed by Joseph Granville and introduced in 1963.

The indicator, together with trend lines, provides good entry/ exit points.
In the chart note the exit point before the crash.
Also, note the "wedge" - a bit lees optimistic that the 'price only' wedge for SPY.