The Fault Lines Reshaping Global Fixed Income

For years, global fixed income rewarded a simple strategy. Hold broadly diversified bonds, lean on US markets to set the direction and let the aggregate do the work.

That approach held up for much of the last two decades as central banks largely moved in lockstep, inflation remained contained and dispersion across bond markets stayed narrow enough for a benchmark to be used as a reasonable way to chart steady returns.

That landscape is now buckling. Last year, global debt surged to a record $348 trillion, according to the Institute of International Finance, squeezing central banks and pulling them out of step with one another. Meanwhile, geopolitical tensions are upending assumptions about just how — and how freely — capital moves across borders. And with nine hyperscalers expected to issue $1.2 trillion in bonds through 2030, the wave of AI infrastructure debt could create hidden exposure for investors across corners of the market. 

The structure of the market is changing, and opportunity is emerging in areas that were once off the map.

US-centered pressures, including the growing weakness of the dollar, questions about US Treasuries’ safe-haven status and the Federal Reserve and European Central Bank moving in different directions, have been widening dispersion across global bond markets. 

The anchors are also loosening beyond the US. Japan, long a source of stability in global bond markets, is now exporting stress. Earlier this year, a selloff in government bonds rippled into US Treasuries. Out of this growing instability is a bond market with more uneven terrain — and, for investors who are able to successfully navigate it, potentially bigger rewards.

This potential is showing up in emerging markets, where hard-currency bonds returned 12.16% in 2025, their best year since 2019, outpacing US bonds by nearly five percentage points, according to Bloomberg. Emerging-market local-currency bonds fared even better, posting their best year since 2009 — with a deeper look at the Global Aggregate finding Mexico and Peru among 2025’s top performers.

Getting those returns requires careful selection. MFS Investment Management’s fixed-income team, for instance, is a strong proponent of diversification and looking beyond domestic borders. The team has positioned itself around high Brazilian currency rates, dislocations in Thailand after recent elections and attractive risk premia in South Africa — a country-by-country reading of dispersed markets, rather than broad benchmark exposure.

“We are strong proponents of diversification in today’s markets, as investors are increasingly looking beyond domestic borders to find opportunities as well as manage risk,” says Pilar Gomez-Bravo, CFA, Co-CIO, Fixed Income, MFS.

In today’s increasingly varied landscape, MFS is pushing investors to look beyond the benchmark. Liquidity becomes the dry powder that lets a manager act when the window opens, but that alone isn’t enough. Investors need to pair flexibility with research infrastructure that can read markets in real time. An investment firm’s goal is to see opportunity before the index can register it, and determine which sectors are breaking from the pack and which countries are repricing under the radar.

The map of global fixed income is being redrawn faster than most portfolios have adjusted, and the pace isn’t slowing. The discipline that works in this environment is more about structure than speed: shared research across a global team; conviction in where to take risk and where not to; and the patience to stay with a process across cycles.

MFS has constructed its platform with that approach, built around collaboration, with regional and sector specialists informing investment decisions. Research paired with liquidity is an edge in a market being redrawn in real time.

“Focusing on geographic diversification, portfolio liquidity and credit quality can help investors manage risks and capitalize on opportunities presented by market dislocations during these uncertain times,” says Gomez-Bravo.

The investors who will do best in the years ahead are those who accept that the ground has shifted and build on what’s still solid.