Nickel alpha-diimine catalysts have been previously shown to perform the chain straightening polymerization of alpha-olefins to produce materials with melting temperatures (T-m) similar to linear low density polyethylene (T-m = 100-113 degrees C). Branching defects due to mechanistic errors during the polymerization currently hinder access to high density polyethylene (T-m = 135 degrees C) from alpha-olefins. Understanding the intricacies of nickel alpha-diimine catalyzed alpha-olefin polymerization can lead to improved ligand designs that should allow production of chain-straightened polymers. We report a C-13 NMR study of poly(alpha-olefins) produced from monomers with C-13-labeled carbons-specifically 1-decene with a C-13-label in the 2-position and 1-dodecene with a C-13-label in the omega-position-using a series of alpha-diimine nickel catalysts. Furthermore, we developed a mathematical model capable of quantifying the resulting C-13 NMR data into eight unique insertion pathways: 2,1-or 1,2 insertion from the primary chain end position (1 degrees), the penultimate chain end position (2(p)degrees), secondary positions on the polymer backbone (2 degrees), and previously installed methyl groups (1(m)degrees). With this model, we accurately determined overall regiochemistry of insertion and overall preference for primary versus secondary insertion pathways using nickel catalysts under various conditions. Beyond this, our model provides the tools necessary for determining how ligand structure and polymerization conditions affect catalyst behavior for alpha-olefin polymerizations.