Mark Massey's Concentrated Portfolio Dominated by Tech Giants

As of December 31, 2025, Mark Massey's portfolio at AltaRock Partners shows significant concentration in a select group of stocks. The analysis reveals that three holdings alone account for over 78% of the total portfolio value, highlighting a focused approach to investment.

The largest position is in Amazon (AMZN), which represents approximately 33.1% of the portfolio. With a substantial number of shares held, AMZN contributes significantly to the overall value. For more details on this position, you can visit the investor profile for AMZN.

Second on the list is Transdigm Group (TDG), holding a 25.28% allocation. This stock, known for its presence in the Industrials sector, is another major component of Massey's holdings. Insights into Transdigm Group can be found here.

Microsoft (MSFT) rounds out the top three holdings with a 19.75% allocation. This Technology sector giant is the third-largest position in the portfolio. Learn more about Microsoft's role in this investment here.

Together, these three stocks—Amazon, Transdigm Group, and Microsoft—comprise the core of Mark Massey's investment strategy as of the end of 2025. Other significant positions include Moody's Corporation (MCO) at 8.16%, Mastercard (MA) at 6.07%, Visa (V) at 3.55%, and Alphabet (GOOGL) at 1.04%.

The data also shows notable changes in share counts for several holdings. Amazon saw a slight decrease in shares held (-3.22%), while Microsoft experienced a significant reduction (-18.95%). Transdigm Group (-0.72%) and Moody's Corporation (-14.15%) also adjusted their share counts during the period.

For a comprehensive view of Mark Massey's investment activities, including complete portfolio breakdowns and historical performance, you can explore the investor profile on Insiderset.