One way to gauge market breadth is to compare the performance of an index where each constituent member is weighted equally to its more traditional, capitalization-weighted counterpart.
When benchmark measures are rising but fewer shares are taking part, that often signals that an advance is nearing its sell-by date.
As far as the S&P 500 index goes, such a divergence has been in effect since late in the summer. That's when the ratio of the equal-weighted version to the conventional version began to roll over.
When it comes to individual sectors, however, there has been considerable variation between them.
Over the past year, for example, the performance of the health care, energy and industrial sectors has been relatively broad-based, while information technology, telecom services and materials group returns have been skewed in favor of large cap shares.
Arguably, because the latter three sectors have lacked the breadth of participation of the former three, that could mean they are especially vulnerable should the market resume the correction that kicked off in mid-October.
Michael Panzner is a 25-year veteran of the global stock, bond, and currency markets and the author of Financial Armageddon: Protecting Your Future from Four Impending Catastrophes and The New Laws of the Stock Market Jungle.
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