There must be something in the air: A lot of investors right now are looking more closely at their asset allocations and wondering whether they need to adjust their portfolios. For example, the Motley Fool Answers mailbag this month holds a query from an investor who -- like many of us -- has some Apple (AAPL 0.36%) shares in his Roth IRA. Good for him, because as we all know, Apple has done pretty well in recent years. But the company is also the biggest holding in the index fund he's invested in through his 401(k), and it's held by a couple of other mutual funds he owns, too. Which leads him to wonder: At what point should he start thinking about reducing his exposure to the tech titan?

In this segment, hosts Alison Southwick and Robert Brokamp weigh in, with some help from special guest Buck Hartzell, director of investor learning and operations at The Motley Fool.

A full transcript follows the video.

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This video was recorded on Oct. 30, 2018.

Alison Southwick: The next question comes from Jim. "Now that Apple is a trillion-dollar corporation, I started digging into how much of it I actually own. When I first started with The Motley Fool, I began building out my Roth IRA and Stock Advisor picks, which included Apple as one of my first Starter Stocks, but it's also the top holding in the index fund in my 401(k) and it's also in a couple of other mutual funds I own. Should I sell my small position in Apple that lives in my Roth to be able to reinvest those funds into another stock that has greater potential to grow? How many Apples is too many Apples?"

Buck Hartzell: A good question, Jim! First of all, congratulations for actually looking. A lot of people who own mutual funds don't understand the concentrations of the funds and there's overlapping kinds of concentrations that can build up. Apple's an obvious one if you own ETFs or mutual funds. They're in just about everything because they're so big and so liquid.

I looked yesterday. Vanguard, if you own the S&P 500; about 4.19% of that mutual fund is in Apple. And then, of course, if you own it in your own portfolios as an individual stock, as well, you can easily get a big percentage that you didn't really know about. So good for checking. If you haven't checked, Morningstar has a cute, little tool. It's called Instant X-Ray or Portfolio X-Ray. Just google "Morningstar" and "X-Ray Tool." You can put in your mutual funds and your individual stocks, and then you can see the overlapping percentages of everything.

So whether you should sell it or not; the nice thing is you have this individual position in a Roth, so you don't have any tax consequences for selling it or not. I'd say that's an individual decision based on what percent you have in there. You didn't tell us that, Jim, but I'd say generally around 10% gets around the high side where you might feel a little bit uncomfortable having that much allocated to it. Like you said, there's no consequences to selling it, so that's fine.

Generally we tell people, though, if you like the company and how well they're performing, don't sell just for the sake of selling, but that 10% is a rough area where you might get uncomfortable.