Historically, linearized methods have been pervasive in the measurement of reactivity ratios for irreversible copolymerization reactions. That is, the differential form of the Mayo-Lewis equation was re-interpreted into various forms to fit reactivity ratios using measurements of monomer conversion from reactions with different initial monomer composition run to vanishingly low conversion. The crux of these methods is the assumption that at low conversion, the feed concentrations of monomer remain relatively constant. As stated previously, these linearized methods have been shown to be systematically inaccurate in the case of irreversible polymerization reactions. Motivated by the wide application of linearized methods to describe copolymerization reactions with reversible propagation mechanisms in the literature, we sought to analyze the general accuracy of such methods. To do so, model copolymerization data were generated with known reactivity parameters and were fit to a linearized form of Eqn. 10 (see the Linearized Methods section of the Supporting Information). The results of this linearized fitting for a test case Fitting of equilibrium copolymerization data between endo-NB and a library of lowstrain cyclic olefins containing endo-cyclic cleavable moieties. The copolymerization was conducted at room temperature in chloroform with an initial monomer concentration of 200 mM and a 1:1 endo-NB to comonomer ratio, with a 200:1 monomer to catalyst ratio. The fitted parameters are listed in Table . For all cases, fitting to the generalized equilibrium copolymerization model gives excellent agreement with data.