Dear all, <br><br>I have been using Gretl recently to estimate proportion of staff, I have three groups and the sum of the three proportion equals to 1. According to Wooldridge (2002) this can of &quot;share&quot; systems can be estimated by SUR models with Feasible GLS estimation (p. 167). Accordingly I can remove one equation. <br>

<br>This is one of the models I estimate<br>&quot;Skill-Mix Gap&quot; &lt;- system<br>equation pNHDfteHT2 const cvnbbeds avgnbbeds nbhospital Found TypeHT_1 TypeHT_2 TypeHT_4 TypeHT_5 gapNCo0305recod gapHCo0305recod gapMCo0305recod <br>

equation pHDNfteHT2 const cvnbbeds avgnbbeds nbhospital Found TypeHT_1 TypeHT_2 TypeHT_4 TypeHT_5 gapNCo0305recod gapHCo0305recod gapMCo0305recod <br>endog pNHDfteHT2 pHDNfteHT2<br>instr const cvnbbeds avgnbbeds nbhospital Found TypeHT_1 TypeHT_2 TypeHT_4 TypeHT_5 gapNCo0305recod gapHCo0305recod gapMCo0305recod <br>

end system<br><br>estimate &quot;Skill-Mix Gap&quot; method=sur --iterate<br><br>The estimation is computed, no problems<br><br>I put iterate but the estimation is done with just one iteration. In the command GRETL reference book I read that with iterate the estimation is the maximum likelihood one. <br>

<br>I am completely lost because I would like to know how does that work, I would prefer to have FGLS as in Wooldridge (my reference book in econometrics). <br><br>There is not so much information around (or at least I have not found it) about how SUR are being estimated. <br>

<br>If someone could help me, that would be great, I am presenting tomorrow and I am a bit nervous, <br><br>Cheers, <br><br>Jean-Baptiste<br>