Monomer addition methodology is provided to adjust monomer addition rates to a polymerization reactor. Advantages of the invention include control of bioabsorbable copolymer structure, improvement of monomer conversion, control of reaction temperature, and reduced reaction time. The overall result is an improved process and enhanced product performance. The technology is particularly useful in the copolymerization of monomers with different reactivity ratios, such as glycolide/lactide copolymers and glycolide/caprolactone copolymers. Monomer reactivity ratios and reaction kinetics are utilized to adjust monomer addition rates.