A series of high-${T}_{c}$ superconductors was studied using soft x-ray absorption spectroscopy at the $\mathrm{Cu}\ensuremath{-}{L}_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ thresholds. From a comparison with CuO and NaCu${\mathrm{O}}_{2}$, it is shown that these superconductors contain mostly ${3d}^{9}$ and ${3d}^{9}\mathit{L}$ ($\mathit{L}=\mathrm{oxygen}\mathrm{ }\mathrm{ligand}\mathrm{ }\mathrm{hole}$) configurations in the ground state, with negligible amounts of $\mathrm{Cu}(\mathrm{III}) {3d}^{8}$. The spectral weights of the ${3d}^{9}\mathit{L}$ components are found to be higher for the Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$-type superconductors than for the ${\mathrm{La}}_{2}$Cu${\mathrm{O}}_{4}$-derived compounds and exceed the values expected from oxygen stoichiometry.