Knowledge center · Factor library
Relative Strength vs. SPY
1-month return relative to the S&P 500, not just in absolute terms.
Formula
t-statistic of the daily return spread (stock minus SPY) over the trailing 21 trading days
Interpretation
Isolates stock-specific strength or weakness from broad market moves — a stock up 5% while the market is up 8% is actually underperforming, and this factor captures that.
What good looks like
Outperforming the broad market over the past month.
What bad looks like
Underperforming the broad market over the past month.
Typical range
Z-scored, capped at roughly ±3.
Limitations
Requires enough overlapping trading history with SPY; unavailable for very recently listed tickers.
How OmniSignal uses it
Separates genuine stock-specific momentum from the stock simply moving with a rising or falling market.
Where it enters the score
Momentum family
References
Standard relative-strength methodology (e.g. IBD Relative Strength Rating)
Related concepts