In an attempt to identify simple, linear correlations describing the activity, we plotted ? @A as a function of 7 , <9=> (Figure , black squares), since the surface amount of B has been related to the activity of perovskites in CO oxidation. However, we do not see a correlation between ? @A and 7 , <9=> . No correlation is observed between ? @A and the parameters 7 ( 89:; , 7 , 89:; , 7 ) 89:; , 7 ( <9=>UVG , and 7 ) <9=>UVG either (Figure ). We have also verified whether ? @A is correlated with the Pauling electronegativity RS of the B element, denoted RS , (Figure , black squares). We observe that ? @A increases, reaches a maximum, and then decreases as a function of RS , . However, there are significant differences in the ? @A values according to the A elements when the B element is fixed. The labels in Figure indicate the B elements associated with the points falling within the respective vertical lines. This shows that the choice of the A element has a significant influence on the activity, in addition to the B element. We identified no clear correlation between ? @A and RS ( or the ionization energy (TR) of the A and B elements (Figure ). In summary, nor the relative amount of A, B or oxygen in the bulk or on the surface neither the elemental properties of A or B elements alone are able to describe the reactivity of the perovskites towards CO oxidation across all the 13 ABO3 materials.