[Limdep Nlogit List] Problem with Inclusive Value parameter inNested Logit Model.

[Mausam Duggal]

Ho,

For starters, what happens if you specify normalization at RU1 instead of RU2. Ru1 is anyways preferred based on Hensher, Rose and Greene, Applied Choice Analysis, A Primer.

Thanks.

Mausam Duggal, MCIP, RPP

Senior Project Coordinator

MMM GROUP

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-----Original Message-----
From: limdep-bounces at limdep.itls.usyd.edu.au [mailto:limdep-bounces at limdep.itls.usyd.edu.au] On Behalf Of ho quoc Chinh
Sent: Sunday, April 12, 2009 2:05 AM
To: limdep at limdep.itls.usyd.edu.au
Subject: [Limdep Nlogit List] Problem with Inclusive Value parameter inNested Logit Model.





Dear all,

I am fitting the Nested logit model with NLOGIT version 3.0.
As a response variable we have eight (08) alternatives. They are: 

None(bundle0), Bike only (bundle1), Motorcycle only
(bundle2), car only (bundle3), Bike and Motorcycle (bundle4), Bike and Car
(bundle5), Motorcycle and Car (bundle6) and All of these three vehicles (bundle7).
All attribute parameters are set to be alternative-specific.

The syntax of the model, which I use, is: 

NLOGIT;
Lhs= BUNDLE;

Choices=bundle0,
bundle1, bundle2, bundle3,bundle4, bundle5, bundle6, bundle7;

    Tree= Car(bundle3, bundle5, bundle6,
bundle7),

    NOcar(bundle0,
bundle1,bundle2,bundle4);

    Model: U(bundle0)=0/

    U(bundle1)=
b2*WORKER+b3*NONWORK+b4*CHILD+b6*INC+b8*PPDENS+b9*DIST/

    U(bundle2)=
b10+b11*WORKER+b12*NONWORK+b13*CHILD+b14*HOUSEOWN

                        +b15*INC
+b17*PPDENS +a2*HEADPRO/

    U(bundle4)=
b28+b29*WORKER+b30*NONWORK+b31*CHILD+b32*HOUSEOWN

                        +b33*INC+b34*MIXLAND+b35*PPDENS
+a4*HEADPRO/

 

    U(bundle3)= b20*HEADPRO/  

    U(bundle5)= b38+b42*INC +b44*PPDENS /

    U(bundle6)=b46+b50*HOUSEOWN+b51*INC+b53*PPDENS+b54*DIST+a6*HEADPRO/

    U(bundle7)=b55+b59*HOUSEOWN+b60*INC+b62*PPDENS
+a7*HEADPRO;

RU2;  

Tlg=0.00001       

$

And
after execution of the model, I obtain the estimates with NEGATIVE Inclusive Value
parameter for Car branch, which can been seen as follow: 

IV parameters, RU2 form =
mu(j|i),gamma(i)

 CAR        
-1.881354099       .11426681  -16.465  
.0000

 NOCAR       
8.594011416       1.1771514    7.301  
.0000

 

What does seem to be the problem? And how should we
understand the negative IV parameter since negative sign of IV parameter is in
fact contrary to the literature. 

Moreover, if we let NLOGIT do the above syntax by itself,
convergence cannot be obtained due to LLF improvement problem. Thus, I have
already employed sequential estimation to obtain the starting value for the
above Nested logit model. 

Any sharing of experience, references or hints are highly
appreciated.

Best regards,

HO, Quoc Chinh.

 

Nagoya
 University, school of
engineering

Faculty of Civil Engineering.

Email: hoqchinh at yahoo.com.vn

            chinh at trans.civil.nagoya-u.ac.jp

 




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