Aggregating oaxaca decompositions of functions of the same variable

Dear all,

Hope you are having a wonderful day! I have a question regarding how to aggregate oaxaca decompositions of a function of the same variable, e.g., how to get the aggregate composition effect of education given that my model has a quartic polynomial.

For example, assuming that my command is

Code:

oaxaca lwage educ educ2 educ3 educ4 urban formal black hispanic

How would I get the total endowments/coefficient (or explained/unexplained) effects for education? I sense that I would only sum the coefficients of educ, educ2, educ3 and educ4, but I don't know what to do about the standard errors. Is there anyway to do this in a straight-forward way?

Thanks in advance and kind regards,
Vinicius.