11. Long-run average return differentials across bonds with different maturities are discussed in Ilmanen, “Does Duration Extension Enhance Long-Term Expected Returns?” op. cit. Near-term expected return differentials across bonds and the time variation in the bond risk premiums are discussed in Antti Ilmanen, “Forecasting U.S. Bond Returns,” Journal of Fixed Income (June 1997), pp. 22–37. A more recent study, Antti Ilmanen, “Stock-Bond Correlations,” Journal of Fixed Income (September 2003), pp. 55–66, focuses on stock-bond correlation as a determinant of bond risk premium but also discusses other determinants.