“…i = 1, … , n, where 1 and 2 denote vectors of coefficients, so that for each group of individuals, represented by x 1i and x 2i , we have possibly different non-default fraction and scale parameters. From (19), we can write the likelihood function of = ( 1 , 2 , ) ⊤ under non-informative censoring as where = (t, , x 1 , x 2 ), t = (t 1 , … , t n ) ⊤ and = ( 1 , … , n ) ⊤ denote the n-dimensional vectors of times-to-default and censoring, respectively, x j = (x j1 , … , x jn ) ⊤ , j = 1, 2, were defined earlier, and f GIWnd (⋅; ) and S GIWnd (⋅; ) are the improper PDF and surviving functions given in (5)- (10). From the likelihood function in (20), the maximum likelihood estimation of the parameter is carried out.…”