st: model question

["Khieu, Hinh" <Hdkhieu@usi.edu>]

Dear Statalist members,
I want to test if X and Y compete for firm resources given a cash flow disruption compared to firms that have no disruption and X and Y are endogeneous. The data are time series and unbalanced.
Is there any problem with the model below?
1/ (X/Y) = a + b1*(disruption)+ control variables, where disruption = 1 if firms receive the disruption and zero if firms do not receive the disruption. Is it correct to say that If b1 is negative, firms receiving disruption do allocate more funds to Y than to X?
Is there a difference between the above specification and the following specifications?
2/ X = a + b1*disruption + b2*Y + b3 * disruption * Y + control variable and this needs to be SUR model using SUREG. Is it correct to say that If b3 is negative, firms receiving disruption do allocate funds to either X or Y, not both.
3/ / X = a + b1*Y + control variable and this is run only for Disruption = 1 again using SUREG. Is it correct to say that If b1 is negative, firms receiving disruption do allocate funds to either X or Y, not both.

I appreciate any comments on the 3 models.

Many thanks in advance.
Regards,
Hinh


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