A partitioning scheme based on the use of density and overlap matrixes of allocating the electrons of a molecular entity in some fractional manner among its various parts (atoms, bonds, orbitals). As with other schemes of partitioning the @[email protected] in molecules, MPA is arbitrary and strongly dependent on the particular @[email protected] employed. However, comparison of population analyses for a series of molecules is useful for a quantitative description of intra-molecular interactions, chemical reactivity and structural regularities.