[Limdep Nlogit List] start=logit with NL
Kandice L. Kleiber
kleiberk at onid.orst.edu
Fri Jul 10 04:26:31 EST 2009
Hi -
I have a few questions regarding the *black box* in NLOGIT. The
nested logit model I have been running looks like this:
tree = cs(corn,soy), wh(wheat), ot(other), and the data does NOT very
across alternatives - only across observations.
Because my nested model is a partially degenerate model, I'm using the
RU1/RU2 commands to normalize. When I use RU1, I add the restriction
IVset:(wh,ot)=1.0. However, when I run the 2 models, they "run"
differently. RU1 begins by running a MNL to get starting values,
while RU2 does not, unless I call start=logit (at least not
explicitly). Even when I use the start=logit command on RU2, the
value of my log likelihood function differs between RU1 and RU2 - from
what I understand, this value should be the same (given the
restriction with RU1).
Should I always include the start=logit command? If not, when should I?
When the command RU2 is used, is the IV parameter NLOGIT reports = (1/
μ)? Or does it report μ?
code:
nlogit;
shares;
tree = cs(corn,soy),wh(wheat),ot(other);
lhs = lev;
choices=corn,soy,wheat,other;
ru2; /*or ru1 with restriction ivset:(wh,ot)=1.0*/
model:
U(corn) = c_c+c_price*price+ ... /
U(cs) = cs_cs+cs_soil*soil+.../
U(wheat)=w_w+w_soil*soil+...$
Any help is appreciated! Thank you!
Kandice.
---
Kandice L. Kleiber
Graduate Teaching Assistant
Department of Economics
Oregon State University
e: kleiberk at onid.orst.edu
w: 541.737.6628
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