With escalating US-Iran tensions and consecutive rate hikes by the European, US, and Japanese central banks, global monetary policy now stands at the threshold of a new tightening phase. Examining ten synchronized global tightening cycles since the 1970s may offer a crucial reference for current asset allocation decisions.

A research report analyzing policy rate data from 104 economies systematically maps out the characteristics and patterns of these ten global tightening cycles. The findings indicate that while the global net hiking diffusion index has recovered somewhat following the late-August escalation of the US-Iran conflict, its overall level remains notably below that of previous typical tightening periods, suggesting the world has not yet entered a phase of fully accelerated tightening.

Against this backdrop, the report argues that US Treasuries present room for increased allocation. Analysts believe the recent surge in Treasury yields reflects a pricing deviation, with markets having already factored in rate hike expectations. Should US-Iran tensions ease, inflation expectations could converge downward alongside falling oil prices, potentially narrowing term spreads further.

Three driving logics identified across ten tightening cycles

Based on movements in the net hiking diffusion index, the report categorizes the synchronized tightening episodes since the 1970s into ten major cycles, grouped into three distinct types. The "anti-inflation" type includes the 2026 US-Iran conflict, the 2021 COVID-19 shock, and the 1978 Volcker rate hikes. These were triggered by external events such as wars or pandemics that caused supply shocks, driving global inflation sharply higher with substantial synchronization among economies. The "cooling an overheated economy" type encompasses the 2010 European debt crisis, the 2008 financial crisis, the 2000 dot-com bubble, the 1997 Asian financial crisis, and the US-Japan-Germany rate hike dynamics following the Plaza and Louvre Accords in the 1980s. These cycles, driven by asset bubbles or debt crises, tended to last longer. The "preventive" type is represented by the US taper of quantitative easing in 2018 and the 1994 Fed tightening, characterized by proactive policy withdrawal after economic stabilization, with relatively limited global synchronization and modest rate increases. Notably, the current cycle falls into the "anti-inflation" category, with the core issue being inflationary pressure stemming from the US-Iran conflict rather than economic overheating or asset bubbles.

The United States remains the anchor for global policy rates

Through a systematic review of tightening paces across eight representative economies and cross-correlation analysis of the leadership roles of the US, European, and Japanese central banks, the report draws several key conclusions. Among the ten tightening cycles, the US participated in all but two (1997-1998 and 2010-2011), and demonstrated clear leadership in five cycles, roughly 63%. Cross-correlation analysis shows that across the full sample, US policy rate changes lead other economies by approximately two months. Since 2000, this leadership advantage has remained robust, with a lead of about one month and a peak correlation coefficient of 0.64. Event studies further confirm that after the US shifts to tightening, the net hiking diffusion index for other economies peaks within roughly three months, indicating a strong triggering effect from US policy cycles. The report also notes that prior to actual US rate cuts, the net hiking diffusion index for other economies often turns negative first, suggesting that market expectations for easing may spread more broadly than for tightening, as markets tend to trade easing expectations earlier. The euro area moves in high synchronization with the global cycle, with a zero lead in cross-correlation and a correlation coefficient as high as 0.85, reflecting resonance with the global cycle rather than unilateral leadership. Japan, however, exhibits a significant lag, with cross-correlation analysis showing a lag of approximately seven months and weaker correlation, attributed to Japan's prolonged negative interest rate policy. Its policy changes also have relatively limited spillover effects on other economies.

Full-scale tightening not yet underway, US Treasuries offer value

Despite consecutive rate hikes by the European, US, and Japanese central banks during the September "super central bank week," the report maintains that this cycle has not yet entered a phase of synchronized, accelerated tightening. The net hiking diffusion index experienced a notable pulse upward in June 2026, but quickly retreated, indicating that tightening momentum has not been sustained. The current index level remains significantly below the peaks of previous typical tightening cycles. The report highlights the transmission chain between oil prices and inflation as a key variable. If US-Iran tensions ease, inflationary pressure could diminish alongside falling oil prices. In this scenario, the report takes a positive view on US Treasuries. Analysts argue that the earlier rise in yields partially reflects pricing deviations, as markets had already anticipated rate hikes. If Federal Reserve Chair Waller's clear communications can reduce the elevated term premium stemming from previous "strategic ambiguity," the valuation appeal of long-dated Treasuries would become more pronounced, and term spreads could narrow.

Three key variables shaping the path ahead

The report identifies three variables that will critically influence the global rate trajectory and asset pricing. First, the US-Iran conflict and uncertainty surrounding US midterm elections. The report points out that the US-Iran conflict may be the core issue at hand. After the signing of a Memorandum of Understanding, overall tightening pressure briefly eased, but with renewed escalation, rising inflationary pressures force major central banks to make more difficult trade-offs between slowing growth and rebounding inflation. Meanwhile, uncertainty over the US midterm elections could affect fiscal policy, debt ceiling negotiations, and the global rate path. Second, the interest rate differential dynamics following Japan's exit from its zero-rate policy. Unlike previous tightening cycles, Japan has now exited its zero-rate policy, with the probability of further hikes continuing to rise. Changes in the US-Japan interest rate differential pose potential shocks to global carry trades and capital flows. The report warns that large-scale unwinding of carry trades could trigger rapid yen appreciation, tighter global liquidity, and heightened volatility in risk assets. Third, the potential influence of the AI industry on rate trends. AI-related financing demand and capital market fluctuations could affect how central banks assess financial conditions and the rate path, making this a new variable that distinguishes the current cycle from historical precedents.