The S&P 500 keeps hitting record highs, dominated by just a handful of stocks that are pushing it to ever greater heights. While that has investors celebrating now, the divergence between the valuations of those companies and some other key metrics has some on Wall Street ringing the alarm about an over-concentration risk.
The top 10 companies in the index make up 35% of the market cap and 23% of the earnings, according to Apollo Chief Economist Torsten Sløk. That disparity is making the S&P 500 is look "more vulnerable" than it has been in decades, he wrote over the weekend.
