Some investors are concerned about over-exposure to Apple stock

Reuters reports that some investors are concerned that their over-exposure to stock in Apple, Microsoft, Facebook, and Amazon could leave them in a sticky position if the market makes any sudden changes in course.

The report has investors concerned about the big four stocks in particular, although it also says that few of them see any concrete reasons for anything to change any time soon.

As the bull market in U.S. stocks hits new highs, some investors are searching for ways to pare their exposure to the small group of technology and communications stocks that has fueled market gains for years.

Just four stocks – Apple, Microsoft, Facebook and Amazon – generated more than 20% of the S&P 500's total return last year, according to data from S&P Dow Jones Indices. Fund managers in a Bank of America Merrill Lynch report in December tagged technology stocks as the market's "most crowded" trade.

While few see a clear reason for their run to end, some money managers worry the market's leaders have become richly valued and overstretched, leaving them vulnerable to a sudden reversal in risk appetite.

While some analysts like Gene Munster believe AAPL could reach as high as $400 in 2020, others are less convinced.

Apple investors have had great success during 2019 thanks to massive growth, but analysts don't expect that to continue through 2020.

"I think most investors… are going to be very surprised by how much risk is in their portfolios when you do get an environmental shift," said Damien Bisserier, partner at Advanced Research Investment Solutions, a Los-Angeles based management and consulting firm managing $13 billion in assets.

The firm has sought to reduce its exposure to potential market volatility by investing in strategies it believes will be less-correlated with stocks, such as funds providing income through healthcare royalties or private real estate investments.