RSP is an ETF designed to track the S&P 500 Equal Weight Index, which holds the same S&P 500 constituents but assigns each company roughly the same weight (about 0.2%) and then rebalances back toward equal weights on a quarterly schedule. That structure reduces the dominance of the largest technology and communication-services names and increases the impact of the “average” S&P 500 stock, which typically makes RSP more sensitive to market breadth and cyclical/value leadership than standard cap-weighted S&P 500 ETFs.

RSP’s gain is most consistent with a “breadth” day in U.S. equities—when more stocks participate in the move—because equal-weight indices benefit when leadership rotates away from a handful of mega-caps and toward a wider set of large-cap stocks. The other key macro input is rates: long-term Treasury yields have been elevated in late March but have also shown meaningful day-to-day swings, and a step-down in yields tends to help the parts of the market that equal-weight portfolios emphasize (industrials, financials, and many mid/upper-mid cap style constituents inside the S&P 500).

First, watch the 10-year Treasury yield direction: if yields resume moving higher, that can compress equity multiples and often re-tightens financial conditions, which can cap equal-weight rallies. Second, watch sector leadership—RSP tends to look best when cyclicals and value-heavy groups lead rather than a narrow tech-driven advance. Third, keep an eye on major U.S. macro releases (notably consumer confidence and other late-month data points) because surprise swings in growth or inflation expectations can quickly change the rates backdrop and the market’s preference for breadth versus concentration.