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Re: st: Re: poisson will not converge


From   Scott Cunningham <scunning@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: poisson will not converge
Date   Wed, 24 May 2006 12:06:10 -0400

On May 24, 2006, at 11:54 AM, Rodrigo A. Alfaro wrote:

Scott,

What is "fip" variable? state? where did you get 55? It seems this variable
is highly correlated with others in the model. A quick inspection could be
helpful: -xtsum rp srfm age2 hgc hhd1 fip-. Moreover, is this panel
balanced?
Rodrigo,

Thank you for your reply. I'll answer what I can.

The panel is balanced (except for hhd1, as I hadn't noticed something before doing the xtsum [see below]). "Fip" is a state indicator variable, and while the number goes to 55, it skips some numbers for reasons only the Census knows so that it still totals to either 50 or 51 (I forget if DC is included separately). You say fip is highly correlated with others in the model. With other variables in the model? You may be right, as when I estimate the model without the - fip- variables, it does converge fine. Also, when I re-estimate the model with fixed effects with just year and fip, it has trouble converging. And this is perhaps due to the fact that there is some migration across time and state within my sample, but not much, as the individuals in the sample are relatively young and most live in the same state. Do you have any suggestions as to what I can do to overcome this? Also, OLS does work fine, making me wonder if I should be suspicious in light of what you said of those estimates.


Variable | Mean Std. Dev. Min Max | Observations
-----------------+-------------------------------------------- +----------------
rp overall | 3.113009 8.069344 0 99 | N = 2283
between | 5.431478 0 44.66667 | n = 761
within | 5.969858 -38.88699 67.11301 | T = 3
| |
srfm overall | 100.1544 11.52157 35.3187 243.9197 | N = 2283
between | 8.116986 53.33359 172.0538 | n = 761
within | 8.180396 46.42766 184.2222 | T = 3
| |
age2 overall | 308.8257 74.43039 169 529 | N = 2283
between | 47.65699 227.6667 443.6667 | n = 761
within | 57.1899 226.159 394.159 | T = 3
| |
hgc overall | 10.58826 1.852228 4 16 | N = 2283
between | 1.33929 5.666667 14.66667 | n = 761
within | 1.280086 7.254928 14.25493 | T = 3
| |
hhd1 overall | .2415459 .4281144 0 1 | N = 2277
between | .3970831 0 1 | n = 761
within | .1596349 -.4251208 .9082126 | T- bar = 2.99212


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