The quantities L ++ self and L -- self capture the ideal or Nernst-Einstein contributions to transport arising from self-diffusion of the cations and anions, respectively. As shown in the middle panel of Fig. ++ self and L -- self vary non-monotonically with slit height, reaching a maximum in the slit with three layers of water. The terms L ++ distinct , L -- distinct , and L +-capture non-ideal contributions to the conductivity arising from correlations in ion motion. For example, correlated motion of cations and anions (such as an ion pair moving together) will result in increased L +-and, by Eq. ( ), decrease the conductivity. These three non-ideal transport coefficients are provided in the right panel of Fig. . We observe that the decrease in conductivity between the bulk electrolyte and the H = 17.29 Å system arises from both small decreases in L ++ self and L -- self as well as increases in the magnitude of each of the nonideal transport coefficients. The drop in conductivity upon further confining the electrolyte is attributed to both decreases in L ++ self and L -- self and increased L +-. In the following sections, we aim to rationalize the trends in each of the Onsager transport coefficients to understand the physical processes contributing to decreased conductivity under confinement. We note, however, that rigorously characterizing transport in confined systems presents some technical challenges. Most notably, the Green-Kubo relations used to compute L ij include a factor of 1/V , where V is the volume of the electrolyte. This volume is not uniquely defined in confined systems due to ambiguities in defining the solid/liquid interface.