st: significance of grouped contributions in Oaxaca decomposition

["Van de Poel, Ellen" <VandePoelE@who.int>]

Dear Stalist users,


 A question regarding the Oaxaca decomposition:
 I use the command : oaxaca group1 group2, de esave
 
 to generate detailed Oaxaca decomposition results.
 
 Thereafter I want to group the contributions of some binary variables
 that result from a categorical one. E.g. I want to group contributions
 from all the (binary) income quintiles to get a general contribution
for income.
 To get the statistal significance of this grouped contribution I use
 the command :
 
 nlcom (wealthcon:
_b[quintile1]+_b[quintile2]+_b[quintile3]+_b[qquintile4])
 
 Now, the problem is that this only works for the "endowments
 contribution". Through the _b[] command I cannot seem to get the
 contributions from the coefficient and interaction effects. Although
 they are visible when I do matlist e(b).
 I cannot set a matrix and e.g. use A[1, columnumber] because then I
 lose the standard errors of the estimates.
 
 I would very much appreciate any helpful suggestion.
 
 Ellen Van de Poel

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