Dear all.
this is the first time I am using SAS to model. I have data from a fish study and would like to use SAS to build a model.
As a first step, I looked in the SAS help and found this interesting example.
I need to understand few things in this example:
1. are the key words 'endogenous' and 'exogenous' mandatory?
2. can I use any instrumental variable that is not correlated to the errors (eq.supply & eq.demand) ?
3. Does it mean that I must have an idea about the model before using this 'proc model' procedure? (i.e. I must know that the error has the following form: eec - (a1 + a2 * eegp )
4. What if I have no idea about the model, the errors or the variable? My study is about the prices of fish and the amount of landings (plus few economic variables: wholesale price, population, income, landings of other competitive fish species, exchange rate...)
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Data for this model is obtained from the SASHELP.CITIMON data set.
title1 'Supply-Demand Model using General-form Equations';
proc model data=sashelp.citimon;
endogenous eegp eec;
exogenous exvus cciutc;
parameters a1 a2 b1 b2 b3 ;
label eegp = 'Gasoline Retail Price'
eec = 'Energy Consumption'
cciutc = 'Consumer Debt';
/* -------- Supply equation ------------- */
eq.supply = eec - (a1 + a2 * eegp );
/* -------- Demand equation ------------- */
eq.demand = eec - (b1 + b2 * eegp + b3 * cciutc);
/* -------- Instrumental variables -------*/
lageegp = lag(eegp); lag2eegp=lag2(eegp);
/* -------- Estimate parameters --------- */
fit supply demand / n3sls fsrsq;
instruments _EXOG_ lageegp lag2eegp;
run;
-------------------------------------------------
Thanks for any hint.
this is the first time I am using SAS to model. I have data from a fish study and would like to use SAS to build a model.
As a first step, I looked in the SAS help and found this interesting example.
I need to understand few things in this example:
1. are the key words 'endogenous' and 'exogenous' mandatory?
2. can I use any instrumental variable that is not correlated to the errors (eq.supply & eq.demand) ?
3. Does it mean that I must have an idea about the model before using this 'proc model' procedure? (i.e. I must know that the error has the following form: eec - (a1 + a2 * eegp )
4. What if I have no idea about the model, the errors or the variable? My study is about the prices of fish and the amount of landings (plus few economic variables: wholesale price, population, income, landings of other competitive fish species, exchange rate...)
---------------------------------------------------------
Data for this model is obtained from the SASHELP.CITIMON data set.
title1 'Supply-Demand Model using General-form Equations';
proc model data=sashelp.citimon;
endogenous eegp eec;
exogenous exvus cciutc;
parameters a1 a2 b1 b2 b3 ;
label eegp = 'Gasoline Retail Price'
eec = 'Energy Consumption'
cciutc = 'Consumer Debt';
/* -------- Supply equation ------------- */
eq.supply = eec - (a1 + a2 * eegp );
/* -------- Demand equation ------------- */
eq.demand = eec - (b1 + b2 * eegp + b3 * cciutc);
/* -------- Instrumental variables -------*/
lageegp = lag(eegp); lag2eegp=lag2(eegp);
/* -------- Estimate parameters --------- */
fit supply demand / n3sls fsrsq;
instruments _EXOG_ lageegp lag2eegp;
run;
-------------------------------------------------
Thanks for any hint.