Market participation
Market Breadth
RSP/SPY is used as the MVP proxy for equal-weight versus cap-weight participation.
Broad market vs biggest companies
This checks whether many stocks are joining the rally, not just the largest names. When this line weakens, the headline index can look healthy while the average stock is struggling.
Equal-weight market vs headline index
Both series start at 100 on the first displayed date, so the gap shows their relative percentage performance rather than different ETF share prices.