According to @KobeissiLetter, only 158 S&P 500 constituents are outperforming the index year-to-date, the third-lowest breadth reading since 1960, with only 1998 and 2023 narrower and a third consecutive year with fewer than 170 outperformers (source: @KobeissiLetter, X post on Nov 24, 2025). Concentrated leadership increases the need to confirm trend durability using cap-weight versus equal-weight gauges such as SPY versus the S&P 500 Equal Weight Index and RSP to assess whether gains are broadly supported or narrowly driven (sources: S&P Dow Jones Indices index methodology; Invesco RSP fund documentation). Traders also monitor the NYSE advance-decline line to validate participation when breadth is thin and to identify potential divergences during rallies (source: NYSE market statistics). Because BTC has shown a higher positive correlation with U.S. equities in recent years, crypto desks track equity breadth as a cross-asset risk-sentiment input when evaluating positioning in BTC and other digital assets (source: IMF 2022 analysis on rising crypto–equity correlations).