STATISTICAL SIMULATION IS IMPORTANT for the design of high-yield circuits, 1 and statistical simulation requires statistical models. Such models can be generated using numerical techniques such as principal component analysis or factor analysis. 2,3 However, physical models have proven substantially more accurate and efficient than strictly numerical models for retargeting statistical models (both for mean shifts and variance shifts in a process), predicting statistical models for a process based on previous generations of that process, and capturing unexpected or anomalous behavior in statistical variations over bias or geometry. The backward propagation of variance (BPV) technique is a unified approach for physically based statistical modeling, for both global and local (mismatch) statistical variations. 4,5 In this article, we present recent extensions and enhancements to the BPV technique. We show how the assumption of a linear dependence of electrical performance on process parameters can be relaxed, and that correlations between different electrical performances can be explicitly included in the procedure. We include measures of circuit performance as modeling targets, andshow that overspecifying the electrical performances to be modeled can improve overall statistical-modeling accuracy.