Termed propagation, it now occurs to the tune of a stupendous 100 million tons per annum. It is therefore no surprise that right from the moment the mechanism of radical polymerization was first elucidated, which was in the late 1930s, there has been strong interest in determining propagation rate coefficients kp. After 50 years of mortal toil, the state of play in this regard was captured by Fig. 1, which presents bulk polymerization values of kp for methyl methacrylate (Y = CH3, X = CO–O–CH3) from the 1989 edition of the Polymer Handbook [1], a compendium of polymer- related data.