Since hitting an interim low on March 5, the NASDAQ Composite index has rallied 10.3%. However, the large cap-laden NASDAQ 100 index has done even better, outpacing the broader benchmark by four percentage points.

In part, the relative outperformance of the narrower measure reflects the fact that investors have increasingly favored large, well-known companies with broad exposure to booming economies around the globe.

More recently, unsettled market conditions have spurred investors to seek shelter in the shares of firms that might fare better than those with less resources at their disposal.

Still, given the near-vertical trajectory of the relative advance and the fact that the NDX (which has an equivalent exchange-traded fund, or ETF (NASDAQ: QQQQ) ) is nearing multi-year resistance relative to the Composite, odds are that the narrower measure is poised to lose a bit of steam, at least in the near term.

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: An Insider's Guide to Successful Investing in a Changing World.

Each week, the Commodity Futures Trading Commission publishes a report known as the Commitments of Traders Report ("COT"), which breaks down aggregate trader positions ( "open interest") in certain futures and options markets into three categories: commercial, non-commercial, and nonreportable.

According to the CFTC, commercial operators, or "hedgers," are "engaged in business activities hedged by the use of futures or option markets." Non-commercial operators, or "large speculators," include individuals and firms, such as hedge funds, that engage in large-scale speculative buying and selling. Nonreportables, or "small speculators," comprise all other participants, including individual traders.

Since bottoming on March 5, the Nasdaq-100 index has been on a tear, gaining 12.77% through yesterday's close.

Yet, if you break things down and analyze the performance of the index's constituent members, it paints a slightly disconcerting picture. Despite upbeat talk from bulls about the health of the market and the rally's sustainability, the advance so far has been narrowly-based.

Apple Inc. (NASDAQ: AAPL), for example, has played a major role in boosting the index, accounting for more than 20% of the upswing. Rallies in three stocks -- Apple, Google Inc. (NASDAQ: GOOG), and Intel Corp. (NASDAQ: INTC) -- comprise nearly a third, while seven stocks are responsible for just under half the gain over the past four months. Finally, only 13 out of 100 stocks, or 13%, account for two-thirds of the overall advance.

While this heavy lifting by a small number of shares doesn't mean the Nasdaq-100 can't go higher still, history suggests that rallies lacking widespread participation sometimes lack long-term staying power.

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: An Insider's Guide to Successful Investing in a Changing World.