By Ryan Vlastelica
NEW YORK (Reuters) - A year ago, Apple had its weight in the Nasdaq 100 cut in half after having grown to where it tipped the scales at more than one-fifth of the index.
The cut didn't last.
Apple, along with a few stocks that have surged in recent months, could soon represent nearly half the index, making this index of 100 well-known companies a hostage to the performance of a few technology titans.
The concentration of Apple, along with others, in the index's market cap-based weighting is exasperating for investors, who don't dispute that Apple should be the biggest weight but bemoan the size of its influence.
"There should be some limitation on how much is held in a particular name," said Mark Bronzo, a money manager at the Irvington, New York-based Security Global Investors, which manages $22 billion.
Apple Inc
A rebalance of the index will be triggered if Apple grows to more than 24 percent, or if the collective weight of all components over 4.5 percent exceeds 48 percent.
Along with Apple, the four names dominating the average are Google Inc
"When you construct an index that is supposed to be a market benchmark, it shouldn't just represent a handful of names," said Bronzo.
Currently, Microsoft is the second-largest component, with a weighting of 9.4 percent, followed by Google (5.5 percent) Oracle (5.3 percent) and Intel (4.8 percent). At the rebalance, Microsoft's weighting was bumped to 8.3 percent from 3.4 percent, and it has grown since.
The five top names add up to 42.2 percent. That's up from 37.3 percent when the index was rebalanced, so their influence is growing but has not reached a point where a rebalance will occur.
"No rebalancing is imminent, and if it happens, people will know about it weeks in advance," said John Jacobs, who runs the Nasdaq OMX Global Index Group in New York.
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For a graphic on the changing weightings of major components: http://link.reuters.com/ceg96s
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Apple's weighting was cut in 2011, as the Nasdaq felt it necessary to give more weight to other names that had shrunk in terms of their influence because of previous rebalancings.
Even with the other stocks taking a bigger part of the average, Apple is still the $500 billion gorilla. The outsized influence of the technology giant means that on days when the Nasdaq sees big swings, Apple is the primary driver.
How much does it matter? The stock's nearly 30 percent gains year-to-date are responsible for essentially all of the Nasdaq 100's 13.4 percent rise in 2012.
"Apple has such a big weighting that it makes fundamentals less important for other names in the index, resulting in an environment where Dell Inc
If Apple stock falls, Schoenberger said, "the whole tech sector is unfairly vulnerable."
This isn't to say the stock's influence on the index is completely out of whack. The Dow Jones Industrial Average <.DJI> is weighted by price, so International Business Machines
Nasdaq OMX Group
Apple's return to a weighting near its previous one has come as its market cap has risen by about 58 percent since April 2011, when the rebalancing first occurred.
Paul Brigandi, vice president of trading at Direxion Funds in New York, said he would support a cut in Apple's weight "for diversification purposes, as concentration in a few names is a concern."
Direxion operates a leveraged mutual fund that is tied to the Nasdaq 100
"Apple has a huge impact on the performance of the fund, and if it corrects that will impact total Nasdaq performance," Brigandi said. "That's a valid concern, and not one we can do anything about."
(Editing by Andrea Evans)