The indicator provides a useful sense of overbought and oversold. More to the point, when values have been in their strongest quartile since 2014, the next 20 days' return has been superior. That's a momentum effect. When the values have been in their weakest quartile, we've also seen a superior average return over a 20-day period. That's a value effect. The trajectory of the cumulative measure acts reflects the cyclical nature of market movement, with returns shifting between value and momentum at various phases of market cycles.