Wall St Week Ahead: Market breadth suggests narrowing rally

The narrow group of stocks powering the market could make it more vulnerable to swift declines if an earnings disappointment or other issue hits its biggest stocks.

NEW YORK: As the S&P 500 has soared to fresh highs, fewer stocks have been participating in the rally, stirring worries that recent gains could reverse if the market’s leaders stumble.

Strong market breadth, or the number of stocks taking part in a broader index’s rise - is often viewed as a healthy sign by investors as it shows gains are less dependent on a small cluster of names.