A shift in economic conditions in which the change in the interest rate on all maturities is the same number of basis points. In other words, if the three month T-bill increases 100 basis points (one %), then the 6-month, 1-year, 5-year, 10-year, 20-year, and 30-year rates all increase by 100 basis points as well. Related: Non-parallel shift in the yield curve.