 However, the issue that these basis functions may be different from those in which the risk decisions were expressed is not widely appreciated.Since conventional risk analysis for fixed-income instruments usually assumes a parallel yield shift across all maturities, it would be most convenient if a parallel motion mode turned out to dominate the other modes, and in fact this is more or less what occurs.While a factor-based decomposition of term structure changes is mathematically elegant, it does have some significant drawbacks for attribution purposes