The Nasdaq-100 PowerShares QQQ ETF (NasdaqGS: QQQ) is also a classic example, with its hefty allocation to tech-giant Apple (NasdaqGS: AAPL). AAPL has also thrown its weight around in other tech-related ETFs, often making up double digit exposure. [Watch Your Apple Exposure in Growth ETFs]

Under QQQ, AAPL is 12.5%, followed by Microsoft (NasdaqGS: MSFT) 7.8%, Google (NasdaqGS: GOOG) 6.6%, Amazon (NasdaqGS: AMZN) 3.9%, Cisco (NasdaqGS: CSCO) 3.4%, Qualcomm (NasdaqGS: QCOM) 3.2%, Intel Corp (NasdaqGS: INTC) 3.2%, Comcast (NasdaqGS: CMCSA) 2.7%, Gilead Sciences (NasdaqGS: GILD) 2.6% and Facebook (NasdaqGS: GOOG) 2.4%.

Source: Morningstar

For more information on ETF indexing methodologies, visit our indexing category.

Max Chen contributed to this article.

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