Cd = Deflection amplification factor
R = Response modification coefficient
Ie = Importance factor
δxe = Deflection

Deflection Amplification Factor, Cd, is defined in Table 12.2-1.

The application of the factor R/Ie to the design response spectrum reduces not only design forces but also displacements. To compensate for this, ASCE 7 requires that the deflections at level x at the center of mass, δx, be determined in accordance with where Cd is from Table 12.2-1, Ie and δxe. Using a value Cd equal to R would result in the displacement δx being equal to δxe, which would be consistent with the equal displacement rule.