Other information technology names Microsoft and Intel were among the top 10 stocks for all generations. That makes the sector a fifth to a third of all portfolio holdings in the study. Google would also be in the top 20 without the stock split.
Next to Apple, the top stocks for the 25-and-under group were Disney and Berkshire Hathaway, demonstrating the influence of entertainment and Warren Buffett on young investors.
Relative newcomer Alibaba, the Chinese e-commerce site, made it into the top 25 holdings for all TD Ameritrade investors under 65, with 25-to-49-year-olds having the greatest allocation. Tesla is also a favorite in that age category.
Sherrod said that age group consists of many working parents who heavily utilize Amazon.com. "The younger demographic is looking at Alibaba as the next Amazon," she said. In a country with a large population and low Internet penetration, they may see it as "a stock that really has room to run."
The data also illustrated age preference for high-beta versus high-yielding stocks. Those under 35 had the lowest allocation to utilities at 1.8 percent, while the 65-plus group had the highest allocation at 4.9 percent. Health-care allocation also skewed higher for older clients.
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CNBC's top ticker look-ups for 2015 to date reflected the study's results. Apple topped the charts, with Facebook and Bank of America the next two most-searched stocks. General Electric followed.