The yield on US government bonds maturing in 10 years — the global benchmark for long-term interest rates. • Benchmark for mortgage rates — rising 10Y = higher borrowing costs • Directly impacts corporate bonds, student loans, and other long-term rates • Below 2%: Low-rate environment, favors growth stocks • Above 4%: High-rate environment, favors value stocks, pressures growth • Above 5%: Extreme tightening (briefly reached Oct 2023) The relationship between the Fed rate (short-term) and 10Y (long-term) is critical. When the 10Y falls below the 2Y, it's called a 'yield curve inversion' — one of the strongest recession predictors.