Measured K-band disc/star flux ratio as function of the fractional luminosity associated with the outer dust reservoir, in the case of solar-type stars. When no outer reservoir is detected, 3σ upper limits are used (dots with arrows instead of diamonds for actually measured fractional luminosities). Stars showing a far-infrared excess only are represented by empty diamond, while filled diamonds correspond to stars showing a mid-infrared excess (disregarding the presence or not of a far-infrared excess).