Activation parameters for propene polymerization mediated by a bis(phenoxyamine)Zr-dibenzyl catalyst in combination with MAO have been measured experimentally and calculated by DFT; experiment and calculation consistently indicate that the entropic term is the most important reason for the low chain propagation rate with this system. Based on this finding and a review of literature data on a variety of olefin polymerization catalysts, we propose a strong correlation between the propagation rate and how catalysts deal with the entropy loss of monomer capture.