The authors present a measurement of the left-right cross-section asymmetry (ALR) for Z boson production by e{sup +}e{sup {minus}} collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider (SLC) during the period 1996--1998. Using a sample of 383,487 Z decays collected during the 1996-1998 runs they measure the pole-value of the asymmetry, A{sub LR}{sup 0}, to be 0.15056 {+-} 0.00239 which is equivalent to an effective weak mixing angle of sin{sup 2}Sigma{sub W}{sup eff} = 0.23107 {+-} 0.00030. The result for the complete 1992--1998 dataset comprising 537 thousand Z decays is sin{sup 2}Sigma{sub W}{sup eff} = 0.23097 {+-} 0.00027.