[Limdep Nlogit List] Marginal effects OP model

[Andreas Drichoutis]

Dear all, 
 
why do the estimation output for  marginal effects after an ordered probit
model appears in the below form? There are no standard errors produced and
this is inconsistent with E22-8 of the manual which illustrates an example
output. The syntax I'm using is:
 
ordered ; lhs=pbofvr ; rhs=w,x ; maxit=4000 
; wts=pweight ; prob=f1 ; marginal $
 
 
========================================================================
||Summary of Marginal Effects for Ordered Probability Model (probit)  ||
||Effects computed at means. Effects for binary variables are         ||
||computed as differences of probabilities, other variables at means. ||
========================================================================
||         Continuous Variable CO_CEN       Continuous Variable TR_CEN
||       ==============================   ==============================
Outcome   Effect  dPy<=nn/dX dPy>=nn/dX    Effect  dPy<=nn/dX dPy>=nn/dX
=======  ==============================   ==============================
Y = 00    -.00083    -.00083     .00000     .00015     .00015     .00000
Y = 01     .00062    -.00021     .00083    -.00011     .00004    -.00015
Y = 02     .00015    -.00006     .00021    -.00003     .00001    -.00004
Y = 03     .00004    -.00002     .00006    -.00001     .00000    -.00001
Y = 04     .00002     .00000     .00002     .00000     .00000     .00000
 
 
 
Regards,
Andreas Drichoutis