Catching Up with Roger Ibbotson: Reflections on Asset Allocation, Diversification and Long-Term Investing

Written by Communications at MASECO

Earlier this month, Josh Matthews, Managing Director, UK & Europe, had the opportunity to meet with Professor Roger Ibbotson during a visit to New York. The two had the pleasure of joining David Booth, Founder and Chairman of Dimensional Fund Advisors, for dinner and an insightful discussion about his new book, Stay Calm: Learn to Embrace Uncertainty in Investing and Life (click here to read our blog reflecting on the evening).

Roger Ibbotson is a Professor in Practice Emeritus at Yale School of Management and is renowned for his research into capital market returns, asset allocation and diversification. His work has played an important role in the development of modern portfolio management and continues to influence investors and advisers globally.

Many of the principles associated with Professor Ibbotson’s work align closely with our investment philosophy. His research has consistently highlighted the importance of asset allocation as a key driver of long-term investment outcomes. MASECO’s approach is similarly underpinned by diversification, disciplined portfolio construction and a commitment to long-term investing, rather than reacting to short-term market movements.

The chart below, developed and made famous by Professor Ibbotson, draws on decades of market history, is a testament to the fact that while short-term returns can be unpredictable, investors who remain invested over longer periods have historically been rewarded. It serves as a powerful reminder of the benefits of patience, discipline, the magic of compounding and staying the course through changing market conditions.

Source: Dimensional Fund Advisors. Past performance is no guarantee of future results. In US dollars. Indices are not available for direct investment. Their performance does not reflect the expenses associated with the management of an actual portfolio. Actual returns may be lower. In USD. US Small Cap is the CRSP 6-10 Index. US Large Cap is the S&P 500 Index. US Long-Term Government Bonds is the Dimensional US 20 Year Treasury Index (Historical). Treasury Bills is: January 1926-December 2025, the Ibbotson US 30 Day TBill TR USD, provided by Morningstar; January 2025-present, ICE BofA US 1-Month Treasury Bill Index. US Inflation is measured as changes in the US Consumer Price Index. CRSP data is provided by the Center for Research in Security Prices, University of Chicago. S&P data © 2026 S&P Dow Jones Indices LLC, a division of S&P Global. All rights reserved. The Dimensional Indices represent academic concepts that may be used in portfolio construction and are not available for direct investment or for use as a benchmark. ICE BofA Index data © 2026 ICE Data Indices, LLC. US Consumer Price Index data is provided by the US Department of Labor Bureau of Labor Statistics.

It was wonderful for Josh to spend time with Professor Ibbotson, and we thank him for sharing his insights and generous contribution to the field of investing.

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