Since, the inverse of the effective mass is the second-order partial derivative of the energy on the k-point in the energy band diagram dividing the square of the Planck constant; the effective mass reflects the degree of dispersity or bending of the electronic energy band. When the value of the effective mass is very large, it indicates that the band is flat and barely diverges at that point in the Brillouin zone, akin to the features of the band structures shown in Figure . Conversely, if the effective mass value is low, there should be high dispersion of the bands in that region of the Brillouin zone. We posit therefor that a 2-dimensional material should exhibit a relatively high conductivity effective mass in the inter-layer direction of a 2D crystal and a relatively low effective mass in the two bonded crystallographic directions. Overall, this behaviour should be possible to capture and quantify in the single value of standard deviation for the conductivity effective mass tensor.