Evolution of the average number of planets per system for different combinations of α and t_init in simulations without migration. The orange and blue lines show the giant planets (≥0.1 M_J ~ 30 M_E) and Earths or Super-Earths (1.0 M_E−0.1 M_J), respectively. The cross, square, and circle correspond to the stellar metallicities of [Fe/H] = 0.5, 0.0, and –0.5, respectively. Giant planets do not form in high-viscosity and low-mass discs. The formation efficiency of all types of planets show some dependency on the stellar metallicity (see text).