Series is calculated as the spread between 10-Year Treasury Constant Maturity (BC_10YEAR) and Effective Federal Funds Rate (https://fred.stlouisfed.org/series/EFFR). Starting with the update on June 21, 2019, the Treasury bond data used in calculating interest rate spreads is obtained directly from the U.S. Treasury Department (https://www.treasury.gov/resource-center/data-chart-center/interest-rates/Pages/TextView.aspx?data=yield).