Yet, when including all monomers back into the fit, also this procedure still yielded an unsatisfactory result. The obvious reason for this is that none of the features sufficiently describes resonance effects, which play a major role in reactivity of monomers. Surprisingly, while qualitative orders of reactivity are obviously known for practically all polymerizable vinyl monomers, no quantitative data on the resonance stability, or radical stability could be found in literature. The closest information that we identified were dissociation constants of macroalkoxyamines, that were determined for nitroxidemediated polymerization from EPR spectroscopy. At least for styrene, acrylonitrile, as well for an average of methacrylates and acrylates, numeric values could be assigned. We normalized these dissociation constants, and provide our best prediction, shown in Figure . Finally. Since this plot yielded a very reasonable fit, we then directly also included the H-binding monomers, as depicted in Figure . Again, it is an interesting observation, that correlation of H-bonding has also a positive predictive effect for example for styrene (the datapoint with the lowest overall k p). As can be seen, both acrylonitrile and styrene (black triangles) fall very well on the line with the (meth)acrylates. r 2 in this case is 0.986, which is a very good result considering that both added monomers have nothing in common with the other monomers in question regarding all other used features. It can be assumed that if actual data for resonance stability of propagating radicals become available for other monomers (such as vinyl acetate for example), that also these monomers can then be adequately correlated. Overall, the ridge regression analysis for weighting of the various features shows that resonance stability by far is the most important feature, overshadowing the importance of dipolar moments and substituent effects.