The article explores how round numbers, like a 5% yield on 30-year U.S. Treasury bonds, can spook investors despite having no technical significance. The recent rise in American long-term borrowing costs—linked to high deficits, political instability, and Donald Trump’s expansive budget—has sparked global concern. As the U.S. economy influences global capital markets, other countries are also seeing rising yields. Germany’s are increasing due to growth-boosting spending, while in Britain and Japan, persistent inflation is the main culprit. Meanwhile, traditional buyers of long-term bonds, such as pension funds, are retreating after locking in favourable returns, further pushing up borrowing costs. If these trends persist, long-term debt could become even costlier worldwide.