Álvarez, Luis J. (contributor); Burriel, Pablo (contributor) - 2005
case of N groups of �rms. In fact, it can be shown
that
h(k)
k
=
N
X
j=1
j
(k)
h
j
(k)
k
+ H(k) (3)
where H(k) =
N … 1
X
j=1
N
X
l=j+1
j
(k)
l
(k)
h
j
(k) h
l
(k)
2
"
jl
(k)
6
Note that the heterogeneity e�ect disappears if the … similar necessary and su� cient condition to have a downward sloping hazard in this
case is
h(k)
k
0 if
N
X
j=1
j
(k)
h …