Diversification benefits, in general, represent an important aspect for calculating a
total SCR for corporate and government bond investments implying interest rate and
credit risk (including spread risk). For our examined bonds, the benefit derived by diversification is up to 40 percent for single bonds and up to 31 percent for the
portfolio of bonds. Thus, diversification is of high importance to the total SCR of bond
exposures.
For investment grade bonds, the largest diversification benefit is achieved by
the Cox et al. (1985) model, however, regarding the diversification in absolute values,
the benefit is approximately equal. Beside the model selection, moreover, the input
parameters of the short term interest rate models are detected as sensitive to calibration.
The starting value and, in particular, the standard deviation are identified as a
significant risk driver and are highly prone to errors in the input calibration.