Solar annulus: top: [α/Fe] (left) and [O/Fe] (right) vs. metallicity, for all stars present today (solid brown curve) and for all stars born in situ (dotted blue curve). Middle: [α]/Fe (left) and [O/Fe] (right) vs. metallicity, for stars of the thick disk (>9 Gyr, green curve) and for stars of the thin disk (<9 Gyr, red curve). They are compared to corresponding data from Adibekyan et al. (2011; left) and from Bensby et al. (2014; right). In the top and middle panels the shaded areas enclose the ±1σ values around the corresponding model averages. The MD data for the thick disk of Bensby et al. (2014) are arbitrarily reduced by a factor of 3 (see text).