The spread between 30-year and 5-year Treasury yields. Measures the slope of the long end of the yield curve.
A steep 5Y-30Y spread signals strong long-term growth and inflation expectations. Compression or inversion at the long end signals deflation fears or demand for long-duration assets.
Steepening (rising spread) favors banks and financials. Flattening or inversion at the long end often leads the economy into slowdown.