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S and p 500
2 guides in Finabase Learn
- Market concentration: what mega caps mean for S&P 500 investors How much of the S&P 500 its ten largest companies now make up, why cap-weighted indexes concentrate, and what it means for an index fund’s risk and diversification.
- Market-wide circuit breakers: the 7%, 13% and 20% halt rules How US stock market circuit breakers work: the three S&P 500 trigger levels, the 3:25 p.m. rule, the four March 2020 halts, and the history back to 1987.
Educational content, not investment advice. Finabase Learn explains how markets and tools work. It does not recommend any security or strategy, and examples are for illustration only. Investing involves risk, including the loss of principal. Rules and figures are for the United States unless stated and can change — check the cited source before you act.