As the final quarter of 2026 begins, global financial markets are contending with robust economic growth and corporate earnings gains that show little sign of abating. This dynamic, largely fueled by a surge in business investment in artificial intelligence (AI) infrastructure, is expected to persist through the end of the decade, compelling central banks—led by the Federal Reserve—to maintain a tightly calibrated approach to interest rate policy.

Deutsche Bank strategist George Saravelos identifies the ongoing AI-driven investment boom as the critical element underpinning current market conditions. He describes it as “superglue” holding together rising bond yields, near-record equity valuations, tight credit spreads, and subdued cross-asset volatility. Historically, large-scale capital expenditure expansions of this magnitude have been rare, with only two comparable instances since World War II: the late 1980s and the mid-2000s. This current wave is shaping up to be the largest in cumulative global spending relative to GDP since 1945.

The combination of inflationary pressures intensified by energy supply disruptions has pushed nominal U.S. GDP growth above 8 percent in the second quarter and is forecasted to surpass 9 percent in the third quarter, according to early tracking. Real inflation-adjusted growth estimates hover around 5.1 percent for the same period, while the Federal Reserve’s preferred inflation gauge, the personal consumption expenditures (PCE) index, is projected to reach 4 percent this month. Approximately one-third of this GDP expansion is attributed to the AI investment surge.

Corporate earnings growth remains robust as the third-quarter reporting season approaches. S&P 500 companies delivered over 50 percent profit growth in the second quarter, with expectations of about 30 percent growth in the third quarter and near 28 percent in the fourth. While the technology, communications, and energy sectors are the primary contributors, other sectors such as materials, utilities, consumer discretionary, and health care are also registering significant earnings increases. Barclays notes that the anticipated full-year 2026 earnings growth rate of roughly 34 percent stands out, given it follows a strong double-digit expansion in 2025, positioning it among the strongest earnings expansions outside of a recovery phase in modern history.

Despite pressure from the White House for looser monetary policy, the Federal Reserve has opted for continued rate hikes—planning up to four more increases in the next year, in addition to the most recent hike. Treasury yields across maturities from three to 30 years have climbed above 5 percent, reaching levels not seen since before the 2007-08 financial crisis.

Yet, some economists question why higher Treasury yields have not significantly tightened financial conditions or slowed economic growth. AXA Group chief economist Gilles Moec points to measures like the Chicago Fed’s National Financial Conditions Index, which suggests that financial conditions remain “accommodative” despite elevated bond yields, contrasting with “restrictive” conditions observed when 10-year Treasury yields last exceeded 5 percent in late 2023. Moec cautions, however, that sustained real economic resilience to high interest rates is unlikely without a marked tightening that activates a feedback mechanism reducing growth.

From an equity perspective, the rise in borrowing costs has eroded stock valuations relative to forward earnings estimates. The S&P 500’s price-to-earnings multiple has dropped to under 19, while the MSCI All-Country World Index sits slightly above 16—levels not seen in nearly three years. Analysts note that these valuation adjustments reflect rising earnings yields matching bond yields rather than signaling a fundamental shift in growth expectations.

Morgan Stanley strategist Andrew Sheets characterizes the situation as a contest against the “denominator” in investment valuations—where "g" represents growth. Over the past three decades, the gap between earnings yields and bond yields has explained a substantial portion of relative asset performance over successive years. Strong growth, driven especially by AI infrastructure investment, encourages investors to maintain confidence despite higher rates. Sheets emphasizes that the critical question is the durability of this rapid growth trend.

If the AI-driven expansion continues and broadens internationally, as current indications suggest, any meaningful moderation in growth—and potentially central bank rate increases—may be delayed until next year or later. For now, the Federal Reserve and global bond markets may need to maintain their cautious stance amid this sustained economic acceleration.