PQ = 1 1 - b + b ??? ( K 1 x 1 + K 2 x 2 + ??? + K n x n ) , wherein x1, x2, . . . , xn are patent indices, b is a parameter of non-linearity, and Ki, i=1, . . . n is a coefficient indicating the relative strength of the contribution of the i-th patent index into the PQc K1+K2+ . . . +Kn=1.