Results for the chemical evolution model in which we consider the density fluctuation by the chemo-dynamical model by MCM13. Upper panel: residuals of the ISM oxygen abundances as a function of Galactic azimuth computed with our chemical evolution model at 4, 8, 12, 16, and 18 kpc after subtracting the average radial gradient. Lower panel: our mock observation to mimic Sánchez et al. (2015) results in which we randomly plot residual ISM oxygen abundance predicted by our chemical evolution at 4, 8, 12, 16, and 18 kpc adding an uncertainty of 5° in the azimuthal component and taking into account [O/H] errors according to Sánchez et al. (2015); the colour-coding is identical to line colours of the upper panel: innermost disc regions are associated with the green points, and outermost ones with the purple points.